[WhiteRL]

All summer long I used the Auto function for Controling the climate in my Truck. It worked just fine. As it cooled down I turned off the auto function and opened up the windows and Sunroof. Of course I have seen an increase in my MPG. This week it has cooled down enough to need some heat in the truck. So I pushed the button for Auto climate control. So I am wondering after fiddling with the Climate control buttons... that even though I am heating the truck it seems as if the AC is running ( When I get out of auto mode the display says AC ON). Is my AC on even though I am heating my truck and will it impact my gas mileage.

 

[shovelhd]

Yes. Hit Auto, set the temp, then toggle the A/C button. You will see the A/C ON switch to A/C off. This setting is the Japanese version of "Heat".

 

[Webwader]

So I am wondering after fiddling with the Climate control buttons... that even though I am heating the truck it seems as if the AC is running ( When I get out of auto mode the display says AC ON). Is my AC on even though I am heating my truck and will it impact my gas mileage.

What I do is turn the Auto function on, set the temp I want, turn the Auto off and hit the A/C button to AC OFF. That way the system functions automatically except that the A/C will not come on. If you need to defrost, just hit the defrost button. The system will switch to Defrost mode and the A/C will come on to aid in defrosting. Just hit the Defrost button again to switch back to normal mode.

 

[Tex's Ridge]

Since yesterday thru the night...rain! This morning we were in the thirties. I had a difficult time defogging the rear window! It was 12 minutes down the before the rear started to clear. Use different modes, temperature settings, defrost button on and off.

 

[captmiddy]

Since yesterday thru the night...rain! This morning we were in the thirties. I had a difficult time defogging the rear window! It was 12 minutes down the before the rear started to clear. Use different modes, temperature settings, defrost button on and off.

Was it actually frost or just fogged up windows? I didn't drive my truck this morning but switched to the Hybrid again since it wasn't raining like crazy so I didn't get to see how the windows looked so I am curious if the problem you had was on actual frost (since it was pretty cold in parts of New England today, enough so that some would have real frost on their windows). If they are just fogged up instead this may be an issue with the windows that even defrosters back there wouldn't have helped much with. I keep a squeegee in my car so I can clear off the back windows, although it is somewhat harder to use on the truck.

 

[Tex's Ridge]

Was it actually frost or just fogged up windows? I didn't drive my truck this morning but switched to the Hybrid again since it wasn't raining like crazy so I didn't get to see how the windows looked so I am curious if the problem you had was on actual frost (since it was pretty cold in parts of New England today, enough so that some would have real frost on their windows). If they are just fogged up instead this may be an issue with the windows that even defrosters back there wouldn't have helped much with. I keep a squeegee in my car so I can clear off the back windows, although it is somewhat harder to use on the truck.

It may have been frost. I did not stop to physically find out. The windshield cleared pretty fast, in the defrost mode.

 

[Skywalker]

Try using the recirculation mode. I found that this heats up the air inside without sucking more moisture from the air outside the vehicle and clears the windows quicker.

 

[djdj]

The A/C is also used to remove humidity from the air. Used in combination with the heater, the air can be kept dry and warm -- especially useful for preventing window fogging.

It can always be turned off by pressing the A/C button, leaving the rest of the climate control in Auto mode.

 

[rtboy1961]

With the heated mirrors, heated seats, and the climate control, the system on the RL is top of the line.
The a/c cycles in auto or defrost mode for 2 reasons. One is to help with defrosting the window. The second is during winter months you would not run your a/c , thus not working its lubricants thru-out the system. So defrost mode will cycle it for that reason. I can not see no difference in gas mileage useing the a/c or not. Even if it did make a difference, I like my comfort and ease of this system so I would let it run its own modes. I know people will argue this point with me,but if you have an engine that is a v-6 or bigger, you will not notice a power loss or gas mileage drop while useing the a/c. I was a ASE certified technician for years and the only cars that showed power loss or slight gas mileage drop were 4 cylinder engines. That goes for any make of auto.

 

[swampler]

With the heated mirrors, heated seats, and the climate control, the system on the RL is top of the line.
The a/c cycles in auto or defrost mode for 2 reasons. One is to help with defrosting the window. The second is during winter months you would not run your a/c , thus not working its lubricants thru-out the system. So defrost mode will cycle it for that reason. I can not see no difference in gas mileage useing the a/c or not. Even if it did make a difference, I like my comfort and ease of this system so I would let it run its own modes. I know people will argue this point with me,but if you have an engine that is a v-6 or bigger, you will not notice a power loss or gas mileage drop while useing the a/c. I was a ASE certified technician for years and the only cars that showed power loss or slight gas mileage drop were 4 cylinder engines. That goes for any make of auto.

Not to argue, but I've been seeing slightly better mileage since the temps cooled off. Not sure if it is engine break-in or lower use of the A/C though.

 

[Webwader]

Not to argue, but I've been seeing slightly better mileage since the temps cooled off. Not sure if it is engine break-in or lower use of the A/C though.

Don't forget that cooler air is denser air and also affects engine performance.

 

[Tex's Ridge]

Don't forget that cooler air is denser air and also affects engine performance.

Could you elaborate for us laymen. How does it affect performance?

 

[Webwader]

Don't forget that cooler air is denser air and also affects engine performance.

Sorry I didn't elaborate Tex. Denser air contains more oxygen and increases the performance of the engine which may account for the increase in mpg. The difference may not be as pronounced into today's engines with air mass sensors and computers as it was in the old carburetor days, but there is probably still some positive effect. When I was a 13yr old kid in Michigan, I had a single cylinder 5HP Allstate motorcycle. The top speed in the summer was 55 mph. Came winter and the nice cold air, and it would do real close to 60.

 

[swampler]

Don't forget that cooler air is denser air and also affects engine performance.

I can also run faster in cooler air too. Don't get as hot and dehydrated as running in summer.

BTW, page 179 of the new O/M (which I finally got my new one today) says: "The air conditioning puts an extra load on the engine which makes it use more fuel. Use the fresh-air ventilation when possible."

 

[GJRUGBY]

Boats are the same way...when the temperature drops and gets colder, the engines run more efficient and produce more HP, based only on the air temp.

I think it is very interesting! And I am not an engineer!

Cheers,
George

 

[jonesy16]

I know this thread has long been dormant, but I wanted to point out that the flip side to the denser air providing more oxygen per unit for combustion, it's also "DENSER" air meaning it requires more power to push the vehicle through it. I generally keep the A/C off in mild months, but I agree that you shouldn't notice a measurable difference in gas mileage on a modern vehicle with the a/c on or off. Hybrids are a different issue.