Alternator whine - but its not the usual suspects....

I've been chasing down an annoying whine on my (new to me) 07 Escalade for about a month now. The whine is 100% alternator related, as if I disconnect the + cable from the back of the alternator, the whine goes away. The alternator also seems to be under stress as I noticed a fair amount of belt rubber on the alternator after only a 100 miles of driving.


I've tried:

* 3x new alternators (AcDelco, WAI)
* A new belt
* A new battery (also bench tested the old battery)
* NO battery (disconnected the battery while the car was running)
* Cleaning the battery terminals & connectors with sand paper
* Cleaning the fusible link and connectors with sand paper
* Cleaning the negative cable that runs from the battery to the engine block passenger side
* Cleaning the negative cable that runs from the back of the engine block to the firewall drivers side.


While narrowing it down to the alternator, I also replaced these so they can be 100% ruled out as culprits:

* Idler pulley
* Tensioners (main and AC)
* Water pump
* Power steering pump

The car has no aftermarket audio or other power consuming devices. The alternators have all been 145A rated.


The car starts, runs and drives 100% fine.

Post a pic or video of the main serp belt tensioner, so we can see where the marks land.

What model number belt are you using for the main belt?

What make and part number for the alternator that's on it in the new pic or video with the tensioner?

The belt I’m using is a Bando 6PK2370, alternator is ACDelco 335-1196 and the idlers and tensioners are all ACDelco too.

In my original post the alternator shown is an WAI as I’d just swapped the ACdelco out for it. But now I’ve reinstalled the ACDelco.

I’ll get a video in a few hours showing everything you said. The belt was a tight fit. I had to fully open up the tensioner and slip the belt over the idler to get it on.

I have an 05 tahoe with an aftermarket system and I had terrible alternator whine for an entire year. Got a ground loop isolator, did the big 3, to no avail. Until the rear end went out and needed work. Had the rear differential, pinon bearing and rear drive shaft worked on and when the work was done, the alternator whine was gone. I read that sometimes alternator whine can be associated with drivetrain issues, so maybe something to consider. Good luck finding what it is.

BigSachsy1 said:

I have an 05 tahoe with an aftermarket system and I had terrible alternator whine for an entire year. Got a ground loop isolator, did the big 3, to no avail. Until the rear end went out and needed work. Had the rear differential, pinon bearing and rear drive shaft worked on and when the work was done, the alternator whine was gone. I read that sometimes alternator whine can be associated with drivetrain issues, so maybe something to consider. Good luck finding what it is.

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That’s a really odd one! Was your whine only while driving?

Jimxms said:

The belt I’m using is a Bando 6PK2370, alternator is ACDelco 335-1196 and the idlers and tensioners are all ACDelco too.

In my original post the alternator shown is an WAI as I’d just swapped the ACdelco out for it. But now I’ve reinstalled the ACDelco.

I’ll get a video in a few hours showing everything you said. The belt was a tight fit. I had to fully open up the tensioner and slip the belt over the idler to get it on.

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ACD 335-1196 is listed as a 160 amp alternator. Since the vehicle is new to you, you may have a engine not correct for the year 2007 escalade and not realize the difference.
The belt should be 6 ribs and about 94 inches long. idler wheels can be replaced without changing the mounting bracket. replacemnt Idler may not be correct. Looks like two choices are available for 2007, one 3.5 inches and one 3.562 inches in diamter.
You may have to find a 2007 Escalade with the same equipment and measure all the drive elements to establish what you have.
The whine sounds like the alternator is putting out a high amp load. A scanner that shows real time data will be helpful with the loads and output of the alternator.

Have you load tested the battery out of curiosity? Ohmed out the cables?

B-train said:

Have you load tested the battery out of curiosity? Ohmed out the cables?

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this was my thoughts. maybe a amp clamp would show that it's under a much heavier load than it should be at idle.

maybe a voltage drop test in a few places would show something. if it goes away when you remove the power wire off the alt. alts can get noisey when fully loaded.

B-train said:

Have you load tested the battery out of curiosity? Ohmed out the cables?

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Yeah I load tested the battery, and have even run the car without the battery connected. If the alternator is whining because its under load, then its something other than the battery thats drawing it. I wouldnt think theres much in a car that could max out a 160A alternator, unless something has gone bad in the starter motor? But then I would have thought it wouldn't operate as normal.

I do have an amp clamp and also a good obd scanner, so hopefully I will be able to get some good data between them.

I'm also going to try and run jump cables direct from the alternator +/- to battery. This should rule out corroded cables.

Someone on facebook asked me if I had 'correctly aligned' the alternator. I've not heard of that before - I simply just slapped it in there and bolted it down. Is there anything I'm not aware of?

I feel like testing the voltage between a few ground to ground points, day alt case to block and neg battery terminal and pos to pos points might help rule out bad cabling and grounds. it's just very common for the cables to be eat up inside and look good. lots of posts about weird electrical issues turn out to be cabling.

the starter shouldn't be involved while the engine is running. but a volt drop test from the pos battery terminal to the starter battery while cranking might give some clues. also alt pos to battery pos with and without some extra load on it from say headlights and ac, and with everything off.

if your obd scanner can read it, it should tell you the DC amp load as well as one of the 2 alt wires in the plug is a return pwm signal to the ecm what the alt load is, so it can compensate idle wise. I'm not 100% sure there's a pid to display it, but it works that way.

this is an interesting one forsure.