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

[Jimxms]

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.

 

[Fless]

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?

 

[Jimxms]

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.

 

[BigSachsy1]

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.

 

[Jimxms]

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.

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

 

[Donal]

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.

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.

 

[B-train]

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

 

[j91z28d1]

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

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.

 

[Jimxms]

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

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?

 

[j91z28d1]

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.

 

[Jimxms]

Ok guys I did some more testing today, and I'm still stumped.

* I sprayed water on the alternator pulley and belt. It didnt make any difference to the noise, making me less suspicious of the belt.

* Then I connected jumper leads (both + and -) direct from the alternator to the battery. No difference. Note: I forgot to disconnect the alternator wire though...so this may be a false test.

* Then i plugged in my OBD2 scanner, and checked the BCM for charging data. It appears to be pulling about 60A:

I wanted to double check this with an amp clamp, but unfortunately I only have an AC one, so it didnt work.

* Then I checked for tensioner markings. I couldn't find anything definitive, so here are some pictures:

* Finally I Ohmed all of the cables and routes that power would take:

Positive Wires
+ Wire that goes from alternator to fusible link = 1.8ohm
+ One side of fusible link fuse to other side of fuse = 3.1ohm
+ Positive battery post to battery side of fusible link = 3.4ohm
+ Alternator post to positive battery post = 10.2ohm

Negative Wires
- Alternator body to chassis post on firewall = 7ohm
- Engine block to random bolt on body = 5ohm
- Battery terminal to engine block = 4ohm

 

[j91z28d1]

sadly the ohm reading doesn't tell you much, even thou some of those do seem a bit high, but could just be the bolt heads and probe not making perfect contact. the meter just runs a small amount of voltage thru the wire, it doesn't give you much idea of what's happening with 60amp running thru it.

this is a simple way to give you good info with just a standard volt meter.

shame about the meter but if the obd reading is correct, 60amps shouldn't really made it whine.

I'm kinda out of ideas. maybe some others can help.

 

[Jimxms]

Bit of an update....I did the "big 3" upgrade using 0/1AWG wire and i think the noise has decreased. It seems to only whine (but at a lower level) for a few minutes at startup and then by the time I'm on the freeway its no longer noticeable.

I guess my question now is: Is everyone elses alternators completely silent? Or is a small amount of whine normal? Other cars I've owned have had zero alternator noise (Corvette, Firebird...etc) but all of them probably have lower power consumption needs.

 

[j91z28d1]

so my yukon doesn't have an alternator. I know, weird hybrid things. but I have also had many gm vehicles and none of the alts made any noise unless battery terminals needed cleaning, and that was more thru the aftermarket radio than under hood.

I do have one of these ungraded gm hairbrush alternators from our trucks swapped onto my c6. these are oem take offs on ebay for 100$. they are direct swap for your truck too, and they are 220amp rating and have more diodes to charge great at idle. I have a DC amp clamp and have seen over a 100 amps at idle with everything on, even with under drive crank pulley spinning it slower. not a single bit of whine from it.

I know you've already tried one new alt, but if it was a auto parts store, you never know what you get and this is a cheap upgrade as well.

the part number you can Google or ebay search is 13536552.

they look like this one. which is the most normal looking one to me. ebay listing's sometimes tag tons of part numbers so there's also a 180amp Delco that's not as good to me that they list sometimes too. it's has different electronics and a one way clutched pulley. no clue why.

 

[Doubeleive]

your problem is ground/power related and doing the big3 confirms that (reduced whine)
usually "audio" whine is because a power and or ground is not isolated enough or a power & ground are too close to each other or something is exposed that shouldn't be
so you might have a exposed wire, pinched wire, a hidden worn spot on a harness, etc.
it could even be a internal fault in the radio or amp.
aftermarket equipment CAN cause it depending on how it was installed (wiring wise)
anything aftermarket installed? fog lights? led/hid headlights, light bar or ANY other equipment?
if so disconnect it and see if anything changes
you can also try and isolate the issue by pulling fuses one at a time for anything not mandatory (lights on the dash won't hurt you) and see if the noise goes away if it does then you know it is due to that system somewhere

i can pretty much assure you it is not due to how the alternator is mounted nor the belt, type size grooves or any other nonsense.
also since you went thru 3 different alternators it's not that either.

basically you are chasing a ground issue or something not insulated properly from other wires/electrical system
best course of action is to probably try what I noted above pull a fuse for something and see if it goes away then go thru each one that you can without causing a drive ability issue.
a good tech with a oscilloscope could probably find it within a couple hours as the whine you hear is a specific electrical signal and will produce a visible waveform

Here are some possible causes of an audible whine and how they might appear on an oscilloscope:

• Power supply noise: This often appears as a low-frequency hum or buzz. On the oscilloscope, you'll see a continuous, low-amplitude wave.
• Switching power supply ripple: This can cause a higher-frequency whine. The oscilloscope will show a series of sharp peaks or spikes superimposed on the DC voltage.
• Ground loops:These can introduce noise that sounds like a buzz or hum. On the oscilloscope, you'll see a random, fluctuating signal.
  
  
• Interference from nearby devices: Electromagnetic interference (EMI) from other electronic devices can cause a variety of noises. The oscilloscope waveform will depend on the specific type of interference
  
  
  
• To identify the specific signal causing the whine, you'll need to:
  
  1. Isolate the source: Try disconnecting different components or devices to see if the whine changes or disappears.
  2. Adjust the oscilloscope settings: Experiment with different timebases and voltage scales to get a clear view of the waveform.
  3. Analyze the waveform: Look for patterns, frequencies, and amplitudes that match the characteristics of the noise you're hearing.

 

[j91z28d1]

I believe he doesn't hear it thru is auto system, I just added that as all I've dealt with. but I think he's alternator itself is so loug you can hear it inside the truck when driving. which seems wild.



on the big 3 setup for these trucks, I've never looked at it only got some of the cars. does it still run thru the factory amp ring thingy?

 

[Geotrash]

Are all of the replacement alternators you’ve installed so far remanufactured?

When I bought my ‘07 several years ago, it had a reman alternator on it that sounded exactly like that. I replaced it with another and it did the same thing. According to the comments on the various vendors’ websites for them, that kind of whine is a common issue with remans. So I replaced it with a newly manufactured unit and it solved the problem. No more whine.

 

[Jimxms]

Are all of the replacement alternators you’ve installed so far remanufactured?

Sadly not, I purchased a brand new AC Delco and WAI unit both from different vendors.

 

[Jimxms]

I believe he doesn't hear it thru is auto system, I just added that as all I've dealt with. but I think he's alternator itself is so loug you can hear it inside the truck when driving. which seems wild.



on the big 3 setup for these trucks, I've never looked at it only got some of the cars. does it still run thru the factory amp ring thingy?

That’s right…well kinda.

I never heard it through the radio until I was listening to an FM station that I drove out of range of. Then, through the static noise I could faintly hear it through the stereo.

Regarding the big 3, yes I kept the grounds going through the battery sensor thing. Tbh I just replaced the wires rather than added more. The only additional ground i added was from engine block to body.

 

[Doubeleive]

That’s right…well kinda.

I never heard it through the radio until I was listening to an FM station that I drove out of range of. Then, through the static noise I could faintly hear it through the stereo.

Regarding the big 3, yes I kept the grounds going through the battery sensor thing. Tbh I just replaced the wires rather than added more. The only additional ground i added was from engine block to body.

in that case are you 100% absolutely sure the whine is from the alternator? have you used a stethoscope to confirm? the most common thing to whine under the hood is the power steering pump followed by the tensioner and idler pulley with everything spinning you pretty much have to use a stethoscope to determine and single out the source of a noise.