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Discussion Starter · #1 ·
Need some input, this one has me baffled...
The engine rpm and all of the lights synchronously 'pulse'. The engine cranks over well, fires right up and usually idles normally for a few seconds then the 'pulsing' starts. The longer it's left running the lower the rpms drop (at that point in the pulsing cycle).
The engine rpms don't surge, they fluctuate between normal idle speed and a few hundred rpm slower. When the engine slows, ALL of the lights dim. Every light on the truck. I know what you're going to say but increasing the rpm to 2k doesn't change the outcome. The lights and engine rpm still pulsate.

The truck ran well last week, then today... bam, a swift kick to the groin. 馃ぃ

No previous running or electrical issues and there aren't any new codes being thrown.

I've attached a video. You can hear the engine load up and unload. When it loads up is when the lights all dim and rpm slows.

I can also smell burning rubber in the area of the serpentine belt after a few minutes of running. None of the bearings feel any hotter than the others

Could this be an Ecu issue? Wiring harness? Alternator on the way out?

Any input would be much appreciated 馃憤

 

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I would put a mechanics stethascope on that alternator and start there. Not many things can cause the entire voltage/headlights to fluctuate like that, cause that sounds, and cause that kind of belt tensioner movement.

The other thing you could try is unplugging the 4 pin connector from the back of the alternator while it's running for a few seconds and see if the sound goes away. Be careful as there is a big positive lead near by that should be covered. Here is an example of doing it to discover a suspected bad diode.(Turn on volume).
 

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Discussion Starter · #5 ·
I would put a mechanics stethascope on that alternator and start there. Not many things can cause the entire voltage/headlights to fluctuate like that, cause that sounds, and cause that kind of belt tensioner movement.

The other thing you could try is unplugging the 4 pin connector from the back of the alternator while it's running for a few seconds and see if the sound goes away. Be careful as there is a big positive lead near by that should be covered. Here is an example of doing it to discover a suspected bad diode.(Turn on volume).
Thanks for the suggestions. I was thinking along the same lines (alternator). I'll have a listen with my stethoscope today. I'll try unplugging the 4 pin connector as well and see what impact it has.

Appreciate the help.(y)
 

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Thanks for the suggestions. I was thinking along the same lines (alternator). I'll have a listen with my stethoscope today. I'll try unplugging the 4 pin connector as well and see what impact it has.

Appreciate the help.(y)
Keep us posted to your progress Koof. The input you have been given is solid.
 
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Discussion Starter · #8 ·
I would put a mechanics stethascope on that alternator and start there. Not many things can cause the entire voltage/headlights to fluctuate like that, cause that sounds, and cause that kind of belt tensioner movement.

The other thing you could try is unplugging the 4 pin connector from the back of the alternator while it's running for a few seconds and see if the sound goes away. Be careful as there is a big positive lead near by that should be covered. Here is an example of doing it to discover a suspected bad diode.(Turn on volume).
So, here's an update... put a stethoscope on the alternator and the bearings sound fine on both drive end and non-drive end.

Checked the battery voltage with the 4 pin connector plugged in & running with no load: It fluctuates from 15 to 17.5 volts, in synch with the pulsing. With A/C on it's steady at ~17v.

Next we unplugged the 4 pin connector from the alternator; low and behold the fluctuations / pulsing / surging stopped. The voltage at the battery dropped to ~13v and slowly continued to slide.

So it seems it may have a bad diode(s)? 17.5v is much too high, no?

I've uploaded another YouTube video for your enjoyment 馃槈.

Ridgeline diode function test
 

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So, here's an update... put a stethoscope on the alternator and the bearings sound fine on both drive end and non-drive end.

Checked the battery voltage with the 4 pin connector plugged in & running with no load: It fluctuates from 15 to 17.5 volts, in synch with the pulsing. With A/C on it's steady at ~17v.

Next we unplugged the 4 pin connector from the alternator; low and behold the fluctuations / pulsing / surging stopped. The voltage at the battery dropped to ~13v and slowly continued to slide.

So it seems it may have a bad diode(s)? 17.5v is much too high, no?

I've uploaded another YouTube video for your enjoyment 馃槈.

Ridgeline diode function test
Great problem solving. For my 06 Ridge, without turning on the lights or air conditioner, the voltage will rise. However I remember somewhere, if the multimeter reads at more than 14.8 volts, then this can be considered as overcharging.
 
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So it seems it may have a bad diode(s)? 17.5v is much too high, no?

I've uploaded another YouTube video for your enjoyment 馃槈.

Ridgeline diode function test
Good job. Not sure if it's bad diodes or voltage regulator. Either way it sounds like you have a bum alternator. The only other possibility I can think of is a bad connection somewhere causing the alternator not to see the voltage it's producing but I think that is highly unlikely.

Rockauto will sell you either a remanufactured or new alternator for $325+ CAD taxes in/shipped/customs/duties..etc. Take about a week. Or find one locally. Be warned though, aftermarket, especially remanufactured ones, seem to have a very high failure rate. Nice thing about one locally is you can exchange it right away once it fails. Hell, I would get them to test the new one in the store if you can.
 
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Discussion Starter · #11 · (Edited)
Good job. Not sure if it's bad diodes or voltage regulator. Either way it sounds like you have a bum alternator. The only other possibility I can think of is a bad connection somewhere causing the alternator not to see the voltage it's producing but I think that is highly unlikely.

Rockauto will sell you either a remanufactured or new alternator for $325+ CAD taxes in/shipped/customs/duties..etc. Take about a week. Or find one locally. Be warned though, aftermarket, especially remanufactured ones, seem to have a very high failure rate. Nice thing about one locally is you can exchange it right away once it fails. Hell, I would get them to test the new one in the store if you can.
Do you know if bench testing the alternator would narrow down or confirm the fault?

Thanks for your help, much appreciated.
 

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Do you know if bench testing the alternator would narrow down or confirm the fault?
Yes. They should be able to confirm if it's failed. I'm not sure if bench testers are equipped to test Honda's dual voltage alternators though.
 
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Discussion Starter · #14 ·
Quick update... the voltage regulator was bad (moisture got inside causing corrosion, as can be seen in the terrible photo). Unfortunately I couldn't source a replacement regulator so ended up buying a new alternator through RockAuto. All is well again, ready for another 300k.

I appreciate everyones input 馃嵒
Fluid Recipe Liquid Gas Wood
 
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