HVAC glitch = 13% worse fuel consumption!

I'm posting this so others won't suffer the estimated 13% loss in fuel economy I endured because of an HVAC control glitch. I put about 14k miles on the truck; divided by an estimated 17mpg average = 823g x estimated $2.70/gal average = $2200; 13% would have saved me about $280!

I've not been overjoyed w/ the overall fuel consumption, but I loved the truck so much that I endured the bad fuel consumption, till recently. About two months ago I changed from a mix of city/freeway to almost exclusively city driving. The truck was just serviced, so all mechanical issues were eliminated. I made an extreme point to drive almost a complete tank full of fuel as if there was an egg between my right foot & the pedal (a trick learned from a vintage Corvette specialist friend). There was every reason for good fuel economy on that tank; no towing, light loads, only mild hills in one trip to Bear Lake, easy on the pedal except for one pass of an American truck (always fun).

14.8mpg on the above tank finally pushed me over the edge to delve into a source for the dismal fuel consumption. I believe I found the source. My next tank achieved 17.8mpg w/o trying. I discovered what appears to be a funky software glitch in the “normal” HVAC control functions.

I’ve had absolutely no reason to use the AC since last fall in CA. Repeated depressing of the button marked “AC” causes the text in the LCD to alternate between “AC ON” & “AC OFF”, obviously self-explanatory. The HVAC system can also be activated by touching either the up or down speed buttons for the fan blower. In this case the LCD lacks any indication of the AC compressor status.

Here’s where “assume” made an ass out of me: I ASSUMED the AC compressor was OFF when the LCD was lacking any indication of the AC compressor status. This is incorrect. The AC compressor can be activated even while the LCD indicates nothing about the AC compressor status. For most of 14k miles, when I thought I was employing only the HV part of the system, I was ACTUALLY employing the AC compressor. This includes many miles driven in very cold north UT, sucking up fuel at a greater rate than what was necessary, for no good reason & w/ no benefit.

How did I confirm? Try it yourself. With the HVAC system off, depress either the up or down fan blower button. The LCD should NOT indicate the AC compressor status. Listen carefully in the garage to the HVAC system noise (open the door so the exhaust doesn't make you sick). Now depress the “AC” button twice so the LCD text reads “AC OFF”. You’ll notice a distinct diminishing of sound caused by the AC compressor turning OFF. It must first be ON before it can be turned OFF! The fact the noise diminishes proves the AC compressor was previously ON, even while the LCD indicated nothing about the AC compressor status.

Double-check for the inverse: Redo the test. Activate the HVAC system by depressing either the up or down fan blower button. Now depress the AC button only once (ON). You will notice no difference in sound. This is because the compressor was already on even when the LCD text indicated nothing about the AC compressor status.

Bummer! Honda owes me $280. Beware! Am I the only idiot who sufferred this malady? Please don't say yes! The remedy is to always activate the HVAC system w/ the AC button, pushing it once if you require AC, or twice ("AC OFF" appears in the LCD) if not. NEVER ACTIVATE THE HVAC W/ NO LCD INDICATION OF THE AC COMPRESSOR STATUS!!!!!!

The software fix should be easy. In any & all cases when the AC compressor is ON, the LCD should indicate such. There should be no case in which the AC compressor is on & such is not indicated in the LCD.

This has been noted here & frankly had I not read those threads, I wouldn't know to tap the A/C button to switch it off when the LCD isn't indicating that it's on. You're right, Honda should correct the indicator programming in software!

Sorry, but this is old news.

When it's in Auto mode you will get no display. If you think that's bad my old tacoma would turn the A/C with the defrost button without turning on the A/C light. Even with the button not pressed.

Sorry, but this is old news.

Man I wish I read it before. DON'T TELL ME THE OWNER'S MANUAL SPELLS IT OUT? PLEASE DON'T TELL ME THAT!

Not good for me here in Florida. I have to use my A/C all the time!

probably part of my problem. I am guessing I don't have the "software" issue with my RT, but I tend to run my AC alot

HVAC otherwise known as climate control is designed to be fully automatic. You set the temperature you want and it does whatever it needs to do to get it there. In cold temperatures the A/C will run to dehumidify the air and help prevent foggy windows ( a safety hazard ). In hot weather, the A/c runs for obvious reasons. When you turn the defrost on, the A/C runs.... this is explained in the owners manual..... that book that you got with your new vehicle purchase. Read it. Aside from that, the A/C doesn't contribute to a tremendous fuel economy loss. Driving style and conditions have much much more to do with it. For an experiment, try taking a road trip in hot weather. Drive one way with the a/c on. On the return trip, keep the windows open and the A/C off. Any guesses as to which will afford the best fuel economy?




HT

Hmmmm... we've had 14.8 MPG and like you, I love my truck so I live with it... but I'm curious now. I'm going in the garage and trying this.

For what it's worth, once I found this out, I now always turn the AC OFF... I have noticed virtually zero change in my gas mileage...:(
But I do average about 16.5 mpg...:)

How'd you come-up with the 13% figure? :confused:
I think more than one tankful difference would be needed...

Hmmmm... we've had 14.8 MPG and like you, I love my truck so I live with it... but I'm curious now. I'm going in the garage and trying this.

PLEASE stay out of the garage with a running vehicle... PLEASE! :eek:

The manual is your friend.

I can't confirm or deny the 13% figure, but I suspect it's pretty close as long as its apples to apples (widows up in both circumstances).

As I've stated before I've never owned a vehicle that runs the a/c compressor as much as the Ridgeline (in Auto mode). I've often noticed that the compressor is running when it's 45 degrees outside and only heat required. The only time the compressor is needed is when cooling or defrost is needed. I've driven a few Ridgeline's and know it's not just a problem with mine. You can override the settings by not using Auto mode when only heat is required.

It takes significant power to run the a/c compressor. The climate control programming seems to run contrary to the normal policies of Honda. It would seem like there's an easy 5% (est) overall fuel economy gain if they would just properly program the climate control system.

It takes significant power to run the a/c compressor. The climate control programming seems to run contrary to the normal policies of Honda. It would seem like there's an easy 5% (est) overall fuel economy gain if they would just properly program the climate control system.
I agree that there's a more than negligible difference in mpg's (AC vs. No AC). I've checked since we had this discussion, months ago.
I also agree that changing the CC program would benefit owners' wallets,
but why would Honda go through a "fix", when they can just do this:

Three seperate mentions (there may be more) in the manual is cheaper... :rolleyes:

HVAC otherwise known as climate control is designed to be fully automatic. You set the temperature you want and it does whatever it needs to do to get it there. In cold temperatures the A/C will run to dehumidify the air and help prevent foggy windows ( a safety hazard ). In hot weather, the A/c runs for obvious reasons. When you turn the defrost on, the A/C runs.... this is explained in the owners manual..... that book that you got with your new vehicle purchase. Read it. Aside from that, the A/C doesn't contribute to a tremendous fuel economy loss. Driving style and conditions have much much more to do with it. For an experiment, try taking a road trip in hot weather. Drive one way with the a/c on. On the return trip, keep the windows open and the A/C off. Any guesses as to which will afford the best fuel economy?
HT

Condescending, but you slightly redeemed yourself w/ some useful content. Maybe you missed my point the first time, so hear it is re-worded.

There are two mutually exclusive information text that appear on the LCD during operation of the Ridgeline "climate control": "AC ON" & "AC OFF". The fact the text exists implies it is useful for the operator to know the difference. Either that, or Honda is notifying the operator of completely useless information, which would therefore make the very same information a safety hazard by nature of it being useless yet visible & likely to be read by the operator, causing a useless distraction. Do you disagree? Please explain your reply. (An example of a safety hazard & ergonomic travesty in modern vehicles is deeply imbedded menus on multi-function controllers, according to every professional road-test opinion. It is innapropriate to require referal to an owner's manual to learn normal functions on a motor vehicle.)

Now...we progress to a third option different from the two above. I explained how every reader (even you) can verify it after about two minutes in a Ridgeline. This option is when the LCD text displays NO INDICATION of the status of the AC compressor, YET the AC compressor is actually ON. Now, if the AC compressor status is worth knowing EVER, then certainly it is worth knowing the AC compressor is ON while the "climate system" is activated.

So, we have established that either:
A) Honda is supplying useful information on the LCD, being whether the AC compressor is ON or OFF when the HVAC system is activated...OR
B) Honda has engineered a safety hazard by sticking utterly useless text in front of the drivers face that distracts the driver from the job at hand, which is operating the vehicle.

Regardless of the above & in addition to it, there is a third condition possible during operation of the HVAC system: That is NO LCD NOTIFICATION OF THE AC COMPRESSOR STATUS, YET THE AC COMPRESSOR IS "ON".

I am firmly in the camp that believes it's absolutely misleading, inappropriate, & a certified Honda screw-up that the Ridgeline allows the above condition to exist.

I'm open to disagreements, but it would help if the position was explained. If the owner's manual refers to the information mentioned here, please note the page. I doubt it enough that I'm not going to even check. I've thoroughly explained the lunacy of the condition, such that if Honda knew about it, it wouldn't exist.

An AC compressor absolutely causes constant, definite, measurable drag on a motor, directly affecting fuel consumption. With no other known change, my consumption jumped from high 14s to high 17s. Readers who don't care about saving $280 annually (about what Honda's screw up cost me), more power to them.

Don't notify me of AC compressor status sometimes, then confuse me by making the status invisible other times. That's the definition of misleading, at the very least.

Honda owes me about $280 by my measure.

I'm curious how others feel. But don't bother w/ irrelevant lectures or useless suggestions to read the owner's manual, unless you find my condition mentioned there. The suggestion to read the owner's manual is ironic, considering the very nature of my complaint is that I've been reading Honda's text on my LCD, which has mislead me to believe my AC compressor was off when in fact it was on.

How'd you come-up with the 13% figure? :confused:
I think more than one tankful difference would be needed...

I agree. I'll keep you posted of future readings. I check every tank. I'd say the overall average mpg w/ about 60% city/40% freeway has been mid-16 to mid-17.

The high-14 mpg tank was all real easy city driving, no load, all flat. My stated purpose was the best city mpg I could get. The high-17 mpg tank was the same + one trip to the lake (50 mins each way), lite traffic, moderate load, 1000' elevation increase/decrease, but another 10-minute 1000' elevation change up a dirt road to check our latest view lot. I'm thinking the drive to the lake was more like city driving than freeway.

But, point well taken...

The scanguage confirms (as does common sense) that the A/C compressor changes the engine load at all speeds. By my very rough calculation I have come up with figures between 7 & 17% differences in engine loads with the A/C compressor running. These comparisons were done on level ground at various speeds with the cruise control running and using the speedometer on the scanguage for speed setting comparisons.

I'm curious to see what kind of mileage I can get now without running the A/C now that I have a full tank of summer gas. I'll bet it translates into 1-2 mpg on the freeway on flat terrain.

I have to agree with Csimo in saying that I have never seen a vehicle that runs the compressor as much as the R/L does. It seems to run literally all of the time no matter what the temperature is. It seems that Honda then uses air flow mixtures to control temperature and humidity vs. cycling on the A/C only when it is needed. A simple reprogramming of the HVAC panel would help mileage tremendously. Why do I say tremendously? If you are only averaging 15 mpg and it helps you to get to 17 mpg, you gain 13% in fuel economy and every bit counts right now.

Yes I know it's a truck and I should expect truck-like mileage but I would rather have that extra money to spend on what I want to, not what Honda's HVAC software wants me to spend it on. Yes I also know that there are vehicles that get better gas mileage but that's not the point. The HVAC software is kinda un-Honda and I like my money and if you say you don't care about mileage, please send me a check or money order for the gas you don't care about so I can put it in my truck.

Sorry, rant off.

I agree that there's a more than negligible difference in mpg's (AC vs. No AC). I've checked since we had this discussion, months ago.
I also agree that changing the CC program would benefit owners' wallets,
but why would Honda go through a "fix", when they can just do this:

Three seperate mentions (there may be more) in the manual is cheaper... :rolleyes:

"The AC indicator does not come on if it was off to start with."
"The AC indicator will not be displayed if it was off to start with."

What does "...to start with" mean? The first time I started the car at the store? That day? The first time Honda started the car at the factory? The problem is extremely esoteric. I know that because it took me a year & 14 mpg to find it. So, if Honda addresses this esoteric problem in the manual, the answer absolutely must be as clear as day, & cover all potential situations, which is not the case in your example. I'm not impressed.

Honda's blunder is not forgiven w/ the use of double negatives above. And it is wrong to have differently worded sentences so close together & with identical meaning.

I'm going in circles here, but this question is extremely relevant & has not been adequately addressed. Is it bad or good for drivers to be informed of the AC compressor status? To the extent it's good it MUST be accurate all the time, not only accurate sometimes & unnacurate other times. If it's useless information it's bad because it's unnecessary & hence only a distraction from the job at hand, which is safely driving the vehicle. The appropriate number of useless distractions to driving a motor vehicle is a definite whole number, which is zero (0). Do you agree or disagree? I acknowledge that spending 28 years responding to ugly vehicle accidents of all stripe increases my sensitivity to these things. That, & I'm a cheap guy, not all the time, but sometimes.

Finally, it is totally, absolutely, positively only arbitrary all the time, that Honda believes it proper to arbitrarily decide sometimes that drivers SHOULD be notified of the AC compressor status, & other times to keep that information absolutely HIDDEN. That is the defintion of "inconsistent" &/or "misleading". This is an indisputable fact for which there is no defense, including noting the problem in the manual. The reason it is the way it is, is because someone at Honda found out late in the design cycle. They arbitrarily decided it was OK rather than re-engineer the software & controls, & put some cryptic inconsistently worded notes in the manual toward the interest of disclosure. They should immediately fix the problem instead.

This is probably not news to anyone: In the old days there was a switch w/ a light that meant the AC is activated. If the light was off & the AC was on THAT INDICATED A MALFUNCTION THAT MUST BE ADDRESSED.

Your example may address only the "defrost" mode, but does NOT address this situation:

Turn on motor, not in an enclosed space
Activate HVAC any method
Set thermostat on LOW
Turn HVAC OFF
Now...touch either the up or down button for the fan speed controllers. Immediately will be heard a small "clunk", which is the sound of the clutch engaging on the AC compressor, a clear signal the AC compressor is now ON. Are we on the same "page"?

The LCD will not indicate this ON status of the AC compressor.

Contrary to the owner's manual page you mentioned, which displays & applies only to the defrost mode, I believe the above condition applies in any & all possible mode settings.

Please correct me if I'm wrong.

Certainly Honda prefers for its customers to not waste hard-earned money on fuel, especially w/ the world oil conditions & our need for foreign oil? Certainly Honda would rather its customer have more money for Honda products & to spend less on fuel?

[QUOTE=ro9397;205090]Condescending, but you slightly redeemed yourself w/ some useful content. Maybe you missed my point the first time, so hear it is re-worded."

:mad: Condescending is right !!!!:mad:

I want to send a BIG THANK YOU to ro9397 :D

There has been mention on this board of a compressor clunk upon starting the truck. The majority of the board members who have a 2006 RL say that we have to live with it. Since I have done the mod that ro9397 suggested, NO MORE CLUNK !!!!!!

I did the A/C test last night on the way home from work and then today when I started up my truck, no clunk or compressor sound at all.

I knew there was a fix to that noise and I am hoping that the MPG on my truck will improve........even a little is worth while. I have also noticed an improvement in the idle. Mine has always had a small shimmy and shake at idle in neutral and in drive that I thought was a little excessive for a new truck.

So thanks again ro9397. Your advice and experimentation into the workings of this much loved truck is greatly appreciated by myself and I hope others.

Toby

When do you hear the clunk. I've noticed a clunk when I put the Ridge in gear and start to drive. First the doors lock and then at the floor board I feel and hear a clunk. Is this the compressor issue you guys are talking about????:confused:

I'm going to experiment with this as well and re-check my mileage.

Best,

Kevin

I just finished a search on the word "clunk" and found over 11 pages and probably more since I perused through the first one only. But the majority talked about the A/C compressor going "clunk" on start up.
One under the heading "Worried", stated that if you turn off the A/C before start up, there is no "clunk".

I am just glad that the noise is gone when I start up my Ridge :cool: .

Toby

I've done this at times, not by design mind you, but all it did was delay the "clunk" until the AC was turned on (mostly while the vehicle was moving, and hence, the sound wasn't as noticeable).

I guess if you can manage to keep the AC off, you wouldn't hear the compressor engage at all. ;) But since I paid for it, I, myself, am going to take advantage of it, and remain comfortable, during the hot summer months especially. :D

The AC HAS helped defog the windshield, on occasion, and for that I'm glad.

Using the "AUTO" function of the RL's Climate Control can be used optionally. Maybe it's just not for everybody.
Knowing when the AC compressor is ON, by some kind of indicator WOULD HAVE BEEN a thoughtful touch by Honda's engineers, however. :rolleyes:

Not good for me here in Florida. I have to use my A/C all the time!

Poor Gonzo... has to use A/C all the time!
I have to use a F**%$# ice scraper half the year!

Every vehicle I have owned with a climate control system (set temp via a control with a digital temperature display) operates basically like the Ridgeline. That includes Mazda Millenia and Jaguar S-type. in addition to other Hondas (Pilot and NSX).

If the system is in full auto (normal), the AC will go on off as the system sees fit. All of these systems have an AC on/off switch which is the only way to prevent the compressor from being used. My Millenia and Jag did not have any indicator to show whether the compressor was engaged or not at any moment in time. My Jag had excellent climate control - the temperature was very stable and I regularly achieved 23MPG at 80 MPH (4 liter V8).

So I don't see why some here are surprised or upset with the RL's behavior.

During the winter here in Texas I had AC off most of the time. I had the worst fuel economy of my ownership of the RL to date during the winter. I attributed that to more cold engine running than usual because I don't think we have winter gas here.

Road & Track said AC typically takes 7 HP to run. They said the old saying about driving with windows down vs. AC on is a myth. Driving with windows down and increased turbulence is less costly to fuel economy than running with AC on.

Road & Track said AC typically takes 7 HP to run. They said the old saying about driving with windows down vs. AC on is a myth. Driving with windows down and increased turbulence is less costly to fuel economy than running with AC on.

The guys over at mythbusters did this same experiment. Their research showed that running the A/C should yield better gas mileage but when they did the experiment, the "windows down" vehicle got the better gas mileage.

I have found that I get my best gas mileage with the windows up, the moonroof tilted up and the back window fully opened and the A/C off.

By total accident, I did my own RL aerodynamic testing. (If you want to call it that.) In an early version of my DIY tonneau cover I didn't correctly glue the black vinyl. I used formica glue. For those of you who don't know. Formica glue is a very strong glue, that is until you expose it to high temperatures. In 80 degree heat and in direct sunlight the surface temperature of my tonneau got up to what I would estimate to be about 140 degrees. At that temperature, the glue melted. (I have since replaced the vinyl and glued the new vinyl with super adhesive weatherstip glue which doesnt have this melting problem.)

Anyways, when I drove the RL on the freeway, the black vinyl seperated from the fiberglass underneath. When driving, a vaccuum is created behind the cab on the RL. This vaccuum created a HUGE bubble in the vinyl formed like I had literally put an air pump under the vinyl and tried to inflate it like a hot air balloon. The bubble would literally get a little over 1 foot high. This bubble was created by all of the low pressure generated behind the cab which translates into aerodynamic drag. The bubble would start to form in different places depending on how fast I would drive.

Just by accident one day I opened the back window while I had the sunroof cracked after this bubble formed. To my amazement the bubble deflated. I could replicate this result at any speed after the bubble had formed.

The bottom line is that opening the back window with the moonroof popped up decreases the low area pressure that is created in the bed and decreases aerodynamic drag. I know that this sounds ludicrous but it is true.

I have often toyed with the idea of putting a piece of plexiglass on the back of my truck that runs from the top of the rear window that matches the contour of the sails that runs down to the surface of the tonneau cover which would totally eliminate the low area pressure created behind the cab. I'd be willing to bet that this "mod" would be good for at least 2-3 mpg. I'd love it if I could get my RL upto 26 mpg on the freeway under ideal conditions.

The more readers must use their AC, the more they should ignore this entire thread. The more readers can drive w/o AC, the more this thread can help save money on fuel consumption. The bottom line is to follow this instruction:
• During HVAC use, to avoid AC compressor drag on fuel economy, "AC OFF" MUST appear in the LCD. Beyond comfort, AC use may assist w/ defogging windows.

The only point to further reading is to more accurately understand the author’s allegations of:
1. Honda’s engineering error
2. Author’s dollar loss

I value this forum, as I also value Honda's general quality. So I'm trying to tread lightly on this subject. I truly appreciate some of the support in this thread...a sincere thank you. This will never be a legal case, & I don't want it to be. I just want to vent a bit. But the posts defending Honda's point of view on this won't be met w/ sympathy by me, because Honda's point of view is incorrect. Honda's point of view cost me money that Honda’s engineering error kept hidden from me. BTW, my above quoted $280 loss is probably too high. I certainly had the AC on intentionally some of those miles. The more accurate figure is between $150-$200 max.

Not one time have I referred to any HVAC setting under the heading of "automatic". Obviously, to me anyway, any use coming under such a heading means the AC status is out of the user's control & is instead relegated to Honda's programming authority. In auto mode users have ceded any authority to complain about the stated problem.

Just to address one last time (hopefully) the page above from the user/owner manual. My stated intent is to put a nail in the coffin of Honda's alleged disclaimer: "...if it was off TO START WITH." (Emphasis added) "It" in the sentence is the AC compressor. The obvious, ludicrous point here is that this implies the status of the AC compressor can always be known "TO START WITH". I have proven & demonstrated unequivocally that there are cases where the AC compressor's ON status is kept secret by Honda's defective engineering. That point is closed now. So I have proven there are cases when the AC compressor status is unknown & unknowable. So in these cases, there is no known accurate indicator of the AC compressor's status "TO START WITH". So we're right back where we started. The instructions are useless to address the wasted fuel from unwanted AC compressor activation.

I apologize that I'm analyzing this to death, but really, there is no defense of Honda's position. Every attempt to defend Honda's position will have the airy holes I've demonstrated, & will continue to demonstrate for readers to judge.

What we have, after thorough analysis, is an AC ON/AC OFF indictor on an LCD. By its very nature & engineering this indicator is only accurate part-time. The other time it is inconclusive & potentially wrong, depending on the software conditions. Anyone defending the correct employment of such a switch in a consumer motor vehicle is incorrect. There is NO CORRECT OR PROPER EMPLOYMENT OF AN INDICATOR SWICTH THAT IS SOMETIMES ACCURATE & OTHER TIMES COMPLETELY WRONG. THAT IS 100% CONSISTENT W/ THE DEFINITION OF A PROBLEM WAITING TO OCCUR. Sometimes it’s accurate, sometimes it’s useless. In any & all other cases, an intermittent indicator is a broken indicator. Putting a couple sentences in a manual doesn’t fix the broken indicator. Example: Let’s say you have a big brightly lit red sign that reads either “OPEN” or “CLOSED” connected to a very important security door. But deep in the instruction manual for the security team is a note that states the light may sometimes show neither “OPEN” or “CLOSED”, yet the door may be open. Can it be debated any more that Honda screwed up? Honda is a great, very smart company, populated by humans who make mistakes. If I was Honda I’d take serious action against whoever signed off on this error.

IMO, the following is the only disclaimer that would be 100% accurate, complete, & acceptable (will never happen, because it would cause more problems that it would solve):

"Preface: All vehicles consume less fuel w/ the AC compressor off; AC may assist w/ defrosting functions.

Honda has strangely managed to both simultaneously over-engineer & under-engineer the control system for the HVAC/Climate Control: Over-engineer because "AC ON" & "AC OFF" may appear in the LCD; under-engineer because there are conditions when the AC may be on while such fact is kept hidden w/o operator performing an esoteric audio test.

Honda doesn’t know about, doesn’t care about, or refuses to spend the money to fix the above described error. The result of the above error is that while the Climate Control is ON or activated, the Ridgeline operator can have certainty of the AC compressor status only when “AC ON” or “AC OFF” appears on the LCD; at all other times the AC compressor status is unknown & unknowable to a non-professional except for performing an esoteric audio test.”

My current position on the subject is this: By its very existence/operation/normal function as described by Honda, the LCD indicator for the AC compressor status is 100% consistent w/ the definition of “defective”, “abnormal”, “broken” or “dysfunctional”. This error cost me about $150-$200 since I purchased the vehicle.

The final answer is the DOT mandating by law a full-time 100% accurate indicator for the AC compressor status (ON/OFF), you know like we lived with for about five decades before ‘puters took over our lives! When it reads incorrect, you know something’s wrong, you know, like I just described above!

I noticed this while sitting in my drive way messing with the stereo. I turned the fan on to move air, but didn't want the AC on. I had noticed that AC OFF wasn't on so I though it wasn't on. UNTIL...I started freezing my A$$ off and hit AC OFF and noticed that the AC was actually on although AC ON wasn't showing.

Didn't think much of it and I now turn the AC off each time I just want outside fan air. By my calculations Honda owes me an extra button push per drive and about $1.87 in gas for the one tank it took me to figure this out.

Bad design on this one...jm2c

Man I wish I read it before. DON'T TELL ME THE OWNER'S MANUAL SPELLS IT OUT? PLEASE DON'T TELL ME THAT!
Or yes, it does. I guess some of you not used to automatic climate control. They all wark like this. It supposed to be totally transparent to the user.

Honda didn't hide anything from you. It's all in the manual, like the answers to 90% of the posts on this forum.

I understand what the complaint is and I understand the cost some of you think you incur. Please do this: Check the price for rebuilding your AC compressor when it starts to leak due to months of inactivity during the winter and then firing it up on a hot spring day.

Or yes, it does. I guess some of you not used to automatic climate control. They all wark like this. It supposed to be totally transparent to the user.

Sorry, they all do not work that way. My 98 Toyota Avalon has a push button AC and an automatic temperature control. If I push my AC button to off, the AC indicator LED light goes out and my system will try to control the car's temperature with just outside air. If the outside air is too warm, the fan blows at high speed forever, or until I turn the AC on.

The other nice feature on the Toyota is that if I shut the car off with the AC off, when I turn it back on, the AC is still off.

Both of my Honda's (Pilot & Ridgeline):

The A/C is on by default unless you manually turn it on.

Unless of course it is in fully automatic mode, then the automatic mode determines when the A/C is on or off.

I understand what the complaint is and I understand the cost some of you think you incur. Please do this: Check the price for rebuilding your AC compressor when it starts to leak due to months of inactivity during the winter and then firing it up on a hot spring day.

The excess fuel consumption is real IMO. Pre-discovery I averaged the 16mpg range about 50/50 freeway/city; seldom cracked the 17mpg range. Post-discovery, last two tanks all city miles, were high 18 & high 19, same driving techniques, no attempt to skew figures. This IMO is NOT a coincidence.

May I inquire how real is the threat you state above? With all due respect my personal experience is that the threat is more perceived than real. I owned maybe a dozen cars w/ AC unused for many months during the winter. Believe me, it never crossed my mind the AC would increase defroster efficiency, & no snow where I lived at that time anyway. I never had a compressor seal fail on any car & have owned at least 25. How do you quantify the threat? How often do you recommend the AC be used to eliminate the threat? Minus any quantification the threat seems more hypothetical than real, IMO.

Thanks.

I guess I will come in on the tail end of this & have not read all the post.
Here is my take on somethings as for use of the A/C it should be used once a week even doing winter. Now that depends on temps. Now with the newer cars this could be some as old as 10yrs when you use the defroster the A/C comes on so you are using the A/C anyway. Back in the old days with my 1980 Honda Prelude with factory installed A/C remember that was an option on cars then. In the 1980 Honda Prelude owners manual it did say you should run your A/C once a week to lube seals. Now I had that car 15yrs & the A/C was working fine just like when it was new. I never had any problem with the A/C. I can't remember what the owners manuals said about the 90 & 94 Accords I had but I did the same with them as I did with the Prelude.
The clunk is known when starting up I have that same issue with my 2000 3.2 ACURA TL. This was a issue widely talked about years ago on the TL boards.
I just turn the unit to the man off fan mode in that car this is not the complete system off. I get no start up clunk then but it sometimes depends on outside Temp.

[QUOTE=ro9397;205090]Condescending, but you slightly redeemed yourself w/ some useful content. Maybe you missed my point the first time, so hear it is re-worded.

QUOTE]



I too agree with RO9397. That was a condescending and fruitless post.

Yes we like the Ridge, but why deny it's faults? You've caved your mind into a narrow path - total bias, almost racism and bigotry against other vehicles.

And your argument ends by pointing towards the manual gives no support what so ever. I would suggest a critical thinking course.

By the way, the $280 can be easily filed from your local jurisdiction for a $35 filing fee. Since the small claims is "small", most corps the size of Honda issues checks without any contests or offer fixes (in this case, there is no fix). The cost for a corporate lawyer is about $850/hr on contract base. So it makes sense that Honda will cut a check of $280 (true costs will be around $400 due to administrative costs in issuing the check) that is well below the counsel costs including taxes etc.

So your true return is $280 minus $35 minus time spent minus efforts = satisfaction.

I would find it difficult to believe that the HVAC running all the time would cost 13% fuel mileage. I am currently testing mine and will make a 280 mile trip today to find out. I would think 3 to 5 % might be a better figure. Just my opinion.

I would find it difficult to believe that the HVAC running all the time would cost 13% fuel mileage. I am currently testing mine and will make a 280 mile trip today to find out. I would think 3 to 5 % might be a better figure. Just my opinion. I guess I'll quote myself. Did 280 mile trip today with the AC in the Off mode and there was NO difference in fuel mileage compared to similar trip in September when we ran the A/C alot. You may have something wrong with your truck.

There are three tests that I know of regarding this issue. All three compared three scenarios:

Scenario 1: Windows up with a/c on.
Scenario 2: Windows down with a/c off.
Scenario 3: Windows up with a/c off.

None of the tests used a Ridgeline of course so the results cannot be directly applied to our vehicles.

The base line of all three tests was scenario #3 (windows up with a/c off).

The first test was done by SAE (Society of Automotive Engineers). Results:
Scenario 2: fuel consumption increased by 8 - 20% depending on the vehicle.
Scenario 1: fuel consumption increased by 5 - 10% depending on the vechicle.

The second test was done by FSEC (Florida State Energy Center). Results:
Scenario 2: fuel consumption increased by 2 - 3%.
Scenario 1: fuel consumption increased by 11%.

The third test was done by Consumer Reports. Results:
Scenario 2: fuel consumption was unchanged.
Scenario 1: fuel consumption increased 3% in a sedan.

Here's some additional detail:
http://www.questline.com/service/document.cfm?id=4363&userid=834859

Overall there is no doubt that running the a/c compressor causes you to burn more gas. How much on a Ridgeline? I don't know, but I believe it would be safe to estimate the loss at approx. 7%.

Overall there is no doubt that running the a/c compressor causes you to burn more gas. How much on a Ridgeline? I don't know, but I believe it would be safe to estimate the loss at approx. 7%.
What is so much fun about percentages is that are like "mill levies" used for taxation in that they don't always translate into real numbers (or dollars).

If you normally get 20 mpg then 7% is about 1 and half mpg. If you normally get 15-16 mpg, then thats about 1 mpg. However, 7% in my Accord is a little over 2 mpg and in my wife's Prius it's about 3.5 mpg.

Since I record and note all fuel comsuption, my results indicate that the 7-10 percent is about right. If I let employees drive my truck, then the "auto" function is always used (and I mean always), then it gets about 15 mpg. When I drive it, I have the "A/C off" about 80% of time and I get about 17 mpg (at this point in time).

Of course one could argue that the driver variable is sufficient in of itself to create the difference. As owner, I'm certainly more concern about fuel expense than employees and therefore drive accordingly.

Hello all. I’m a new Ridgeline owner and have been surfing these forums and gleaning all kinds of great info from what is definitely a very knowledgeable and enthusiastic bunch of folks. So first let me say thanks all for the great tips and buying advice, and thanks to the forum staff for putting together such a wonderful Ridgeline resource.

That said, I was reading this particular thread and was worried that there might be a problem with my new truck’s climate control system. (HVAC Glitch = 13% worse fuel consumption!!) The author is very convincing and even had some other comments thrown by members like “known issue,” “programming error” “yea I got cold air,” etc.

Being a maintenance toad myself I thought I would dig into this issue of a “glitch.” Especially since other new members/owners might read this thread and believe “glitch.” So, I thought I’d take a moment and maybe contribute a little something back to this outstanding place and maybe help some fellow new owners. You veterans can stop reading here as many of you have probably already seen right through the original posters allegations, but I was pouring over this thread worried of an actual problem because of my own unfamiliarity with the new truck’s system.

So for my fellow new owners here ya go,

First, the original poster of this thread said there is a “glitch” in the climate control system and went into great detail concerning his opinion of the design and the lack of a compressor state indication in the LCD. This "lack" of an indication and a misunderstanding of the system caused him to make certain assumptions that ultimately impacted his wallet. While he was addressed by a Honda tech, some mild RTFM comments and some pointers, he doggedly carried on with his original assertion of a design flaw and this has gone mostly un-checked. Again, just want to clear this up for any potential buyers or new owners seeing this thread and assuming a “design flaw.”

I have an RTL so I’ll just be referring to the specifics of its system.

On the RTL (this will also apply to RTS I believe) we have three distinct modes of operation as pertains to the climate control system. I use the term “mode” loosely here as Honda calls the vent control (air direction) “modes.” I’ll try not to confuse the two meanings.

Auto: climate controlled automatically (includes the compressor) and the word AUTO is displayed in the LCD. So, you will notice no fan speed, vent direction, or compressor status displayed in the LCD as these are all being automatically controlled.

Semi-Auto: compressor controlled automatically by default, and the operator has assumed control over one or more elements of operation i.e. fan speed, mode (vent control), or the compressor. The LCD will no longer display AUTO and the manually controlled element now appears in the display, e.g. fan speed.

This is the bit where a little misunderstanding exists. Some operators have assumed they are in full manual operation because the words AUTO are no longer displayed and are looking for a compressor status, saying there is none. The compressor status is not displaying AC ON or OFF in the display so, you can denote that it is in fact still controlled automatically.

So, the overall theme here is, elements of the climate control system that are being manually controlled display on the LCD so that the operator has a visual indication of the state of the manually controlled element. Items not showing are in automatic mode.

If you turn the HVAC system OFF and then turn it on via the fan speed buttons for instance, you’ll notice that you will automatically be placed in Semi-Auto and the compressor is controlled automatically by default in this mode (i.e full range temperature control enabled via the temp control dial). Again, you can denote this by the LCD display NOT showing a status of the compressor, e.g. AC ON/OFF.

The assertion that the design team failed us by not putting a constant compressor indication can be argued I guess, but I would say that the AC ON/OFF display NOT showing is an indication in and of itself. It indicates automatic control.

Manual: We enter manual control of the compressor by pressing the AC button. The words AC ON or AC OFF now appear in the LCD indicating that manual control of the AC compressor has been assumed by the operator. Temperature selection is still fully operational, but in AC OFF the range of temperatures the system will be able to achieve is obviously limited to near ambient or greater. Press one of the Fan Control buttons, and then Mode button and now the operator has full manual control of the entire climate control system.

I hope this might be useful for someone and I apologize for the wordiness, just trying to be clear and dispel any myth of a “glitch.”


Cheers,
James

I hope this might be useful for someone and I apologize for the wordiness, just trying to be clear and dispel any myth of a “glitch.”
Cheers,
James
OK, then how about counterintuitive? :eek:
I have an Accord that does the same thing and I had to read it here to figure it out.
BTW: thanks for the explanation. It is appreciated.
The fact that it takes a long explanation underscores how counterintuitive the operation really is. :D

I leave mine in Auto 99% of the time. The problem that I have with the system is that the system is programmed to run the compressor when it's not necessary.

Yes, it's necessary to run the compressor every so often in the winter to keep everything properly lubricated, but there's no need for the compressor to be running most of the time.

I've never had a vehicle that runs the compressor as much as the Ridgeline does.

When it's in Auto mode you will get no display. If you think that's bad my old tacoma would turn the A/C with the defrost button without turning on the A/C light. Even with the button not pressed.

My 06 PILOT LX did this, I searched and found the "program" reset and now light illuminates w/ front window defrost selected. It would also remain engaged if the selector was moved to feet/dash etc w/o ac illumination. I only new this from my 01 accord.

I'm posting this so others won't suffer the estimated 13% loss in fuel economy I endured because of an HVAC control glitch. I put about 14k miles on the truck; divided by an estimated 17mpg average = 823g x estimated $2.70/gal average = $2200; 13% would have saved me about $280!

I've not been overjoyed w/ the overall fuel consumption, but I loved the truck so much that I endured the bad fuel consumption, till recently. About two months ago I changed from a mix of city/freeway to almost exclusively city driving. The truck was just serviced, so all mechanical issues were eliminated. I made an extreme point to drive almost a complete tank full of fuel as if there was an egg between my right foot & the pedal (a trick learned from a vintage Corvette specialist friend). There was every reason for good fuel economy on that tank; no towing, light loads, only mild hills in one trip to Bear Lake, easy on the pedal except for one pass of an American truck (always fun).

14.8mpg on the above tank finally pushed me over the edge to delve into a source for the dismal fuel consumption. I believe I found the source. My next tank achieved 17.8mpg w/o trying. I discovered what appears to be a funky software glitch in the “normal” HVAC control functions.

The software fix should be easy. In any & all cases when the AC compressor is ON, the LCD should indicate such. There should be no case in which the AC compressor is on & such is not indicated in the LCD.


Thanks so much for posting the glitch! I must have the same problem and so glad it wasn't more. I'll check it out and report back but it sounds the same. One would think Honda would simply tell us of the problem or give special information including same......Love the vehicle too,
Regards
Cajunboy

I've always heard the compressor come on whenever I use the up arrow to turn on my heat, I just thought it was a Honda thing. I wonder if I'll even see a difference.

I say to BS that the A/C is to blame for bad MPG. Sounds like driver error to me ???

I say to BS that the A/C is to blame for bad MPG. Sounds like driver error to me ???

It's not. Tested it this morning. Still got horrible mileage.

You work AMMO by any chance?

This issue isn't limited to Honda. "Most" post 1990 cars operate in this manner. If you have Auto climate control it's virtually guaranteed to work this way. Part of the thinking is that it does dehumidify the air to reduce fogging of windows. The other part is that people would not run their A/C units all winter and then have a freon leak in the spring when they turn it on. It was the manufacturers way of forcing the A/C to be cycled during the winter months and preserve the seals.

I think you guys are making a big fuss over this. If you live in a cold climate (and I am talking like below freezing 32F) and you have to let your truck idle for 30 minutes just to reach a decent drivable temperature. That is where your fuel is going. (Honda... give us a engine block heater) I live in Arizona and I still let my truck idle in the morning to warm up. In fact I tell most people that if they have not operated their vehicle in the last 8 hours to let it warm up. I run my AC 100% of the time. My reason for this is that the truck comes with air filtration and if you have ever been to Phoenix. Our air is horrid. So I run the system all the time and just turn the temperature dial to where it comes out comfortably. I get a solid 17.5MPG here in Phoenix and when I was in Colorado I was getting 22.5. Now... is the Compressor to blame? No... I believe that since the average altitude in Colorado is 6500-6800 feet that the air is so thin it allows the vehicle to pass through it easily. The average altitude in phoenix is 1100 feet. I even took the ridge with a full tank of gas from Colorado Springs to the top of Pikes Peak and back and got 24MPG.

Now... I agree that the Compressor does put drag on the motor but I have a very... very hard time believing that it would be enough drag to go from 18 to 14, 17 to 14 or even 16 to 14MPG. Also its not like the Ridgeline is trying to start a giant piston on the inside of that compressor. I have not taken one apart but I am pretty sure it is about 6 little tiny pistons inside of the compressor like most all compressors on vehicles. It is easier to turn 6 small pistons than one large one. Now for a little education on HVAC. An HVAC system removes heat from the air inside your RL and rejects it to the air outside your RL via the evaporator and the condenser. Now... if you live in a cold climate and its cold outside(below 50ºF, R134a at 50ºF is at 45psi) and the compressor is running it is barely doing any work. The reason for this is because there is very little HEAT in the air to remove. It would only have to compress the gas to 80ºF(85psi) for it to effectively remove heat So the system barely has to work at all. If the compressor was running it would be far less drag on the motor compared to a compressor that is running in 120ºF in the middle of summer.

If it is 120º F outside... the compressor has to compress a fluid that BOILS AT -26.6°C (-15.88ºF) to 150ºF (265psi)for it to remove heat from your vehicle effectively.

I am not saying that there is no glitch, I am just saying that it would be hard pressed that the HVAC System would be so parasitic to the RL's power plant.

If you had the fortitude to read my post and understand its meaning. Then you should realize that there must be more than one cause to your fuel malady.

-Fett

P.S. I work in the HVAC/R Industry.

More vehicles than not have been running the compressor all the time since the 70s. Not uncommon at all. Most have no way to disengage it. Our ‘79 caddy had a ECON button you could push to drop the compressor out. I was always told it ran to dehumidify the cabin air. I’ve also been told that the fastest way to get heat is to run the AC on full with the temp all the way up. That won’t help for defrosting if you need to….just heat. At any rate, Honda is no different from any other car in that regard.

To my knowledge, all vehicles the last 30 years or so shut the compressor down at WOT to add HP to the equation. You can easily find that out by mashing the pedal and see if the ac stops blowing cold air. I would be very surprised if the RL wasn’t programmed the same way given the power equation they tried to balance.

Honda gearing. Done deal. With a 4.53 final drive ratio and 1.07 3rd ratio (the 1to 1 equivalent for other cars)…..it is not possible to get good MPG with these ratios. 4th and 5th are both OD gears. That’s where any MPG comes from, but also why 5th ranges in and out on slight grades. .53 is a big time OD gear. The 4.53 is needed to help it out and also to haul 5000 pounds in 3rd gear.

Winter time. NO vehicle needs to warm up for more than a couple minutes, no matter the temperature. Moving the vehicle is the best and fastest way to get the engine up to operating temperature and is also MUCH better for the engine.

Idling for a long time is flat out not the best way to warm up the engine. You could not run an engine for 6 months and a couple minutes of running before moving is all that's needed...oil pressure being the key parameter.

I do agree that idling is the biggest user of gas when cold or hot.

You work AMMO by any chance?


C141B/C17A Crew Chief 20+ years :act035:

I think you guys are making a big fuss over this. If you live in a cold climate (and I am talking like below freezing 32F) and you have to let your truck idle for 30 minutes just to reach a decent drivable temperature. That is where your fuel is going. (Honda... give us a engine block heater) I live in Arizona and I still let my truck idle in the morning to warm up. In fact I tell most people that if they have not operated their vehicle in the last 8 hours to let it warm up. I run my AC 100% of the time. My reason for this is that the truck comes with air filtration and if you have ever been to Phoenix. Our air is horrid. So I run the system all the time and just turn the temperature dial to where it comes out comfortably. I get a solid 17.5MPG here in Phoenix and when I was in Colorado I was getting 22.5. Now... is the Compressor to blame? No... I believe that since the average altitude in Colorado is 6500-6800 feet that the air is so thin it allows the vehicle to pass through it easily. The average altitude in phoenix is 1100 feet. I even took the ridge with a full tank of gas from Colorado Springs to the top of Pikes Peak and back and got 24MPG.

Now... I agree that the Compressor does put drag on the motor but I have a very... very hard time believing that it would be enough drag to go from 18 to 14, 17 to 14 or even 16 to 14MPG. Also its not like the Ridgeline is trying to start a giant piston on the inside of that compressor. I have not taken one apart but I am pretty sure it is about 6 little tiny pistons inside of the compressor like most all compressors on vehicles. It is easier to turn 6 small pistons than one large one. Now for a little education on HVAC. An HVAC system removes heat from the air inside your RL and rejects it to the air outside your RL via the evaporator and the condenser. Now... if you live in a cold climate and its cold outside(below 50ºF, R134a at 50ºF is at 45psi) and the compressor is running it is barely doing any work. The reason for this is because there is very little HEAT in the air to remove. It would only have to compress the gas to 80ºF(85psi) for it to effectively remove heat So the system barely has to work at all. If the compressor was running it would be far less drag on the motor compared to a compressor that is running in 120ºF in the middle of summer.

If it is 120º F outside... the compressor has to compress a fluid that BOILS AT -26.6°C (-15.88ºF) to 150ºF (265psi)for it to remove heat from your vehicle effectively.

I am not saying that there is no glitch, I am just saying that it would be hard pressed that the HVAC System would be so parasitic to the RL's power plant.

If you had the fortitude to read my post and understand its meaning. Then you should realize that there must be more than one cause to your fuel malady.

-Fett

P.S. I work in the HVAC/R Industry.

Like many "better" systems, the Ridgeline uses a variable-displacement compressor. This allows the compressor to remain engaged as opposed to having to cycle on and off like "cheaper" systems. This design results in smoother operation and longer clutch life. Even though the compressor is running, at low heat transfer demand very little engine power is used.

Like many "better" systems, the Ridgeline uses a variable-displacement compressor. This allows the compressor to remain engaged as opposed to having to cycle on and off like "cheaper" systems. This design results in smoother operation and longer clutch life. Even though the compressor is running, at low heat transfer demand very little engine power is used.

variable-displacement compressor? please explain on the mechanics. if the compressor remains engaged then there would be no need for a clutch.

variable-displacement compressor? please explain on the mechanics. if the compressor remains engaged then there would be no need for a clutch.

Google "variable displacement compressor" to learn more about them. They've existed for many years. They vary the stroke of the pistons (using a swash plate, wobble plate, or cam - depending on what you want to call it) depending on demand. Once a "call for A/C" is initiated, the compressor clutch remains engaged as opposed to cycling on and off to maintain evaporator temperature. Most designs have a minimum stroke or "displacement", so there is still a need for an electromagnetic clutch to completely disengage the compressor when there is no call for A/C or when a low or high pressure condition exists.

Ah okay, cool..

I also have not been able to duplicate this glitch. The last two days I have noted that my display either says AC On or AC Off.

Maybe my 08 RTX has the software upgrade!

Google "variable displacement compressor" to learn more about them. They've existed for many years. They vary the stroke of the pistons (using a swash plate, wobble plate, or cam - depending on what you want to call it) depending on demand. Once a "call for A/C" is initiated, the compressor clutch remains engaged as opposed to cycling on and off to maintain evaporator temperature. Most designs have a minimum stroke or "displacement", so there is still a need for an electromagnetic clutch to completely disengage the compressor when there is no call for A/C or when a low or high pressure condition exists.

Good explanation zroger. It might be helpful to note that when using a variable displacement compressor or in my world a "pump", that when there is no demand and the pump is idling along at near zero displacement and minimum pressure there is really no HP demand ((disp*psi)/constant)=hp.