Whining alternator driving me crazy, tried everything

[Doubeleive]

Do you mean straight from the output terminal to the battery terminal? So that there are 2 wires coming from the output terminal? And would it go on the positive or negative battery terminal? I'll have to get a shop or a buddy to help me with that one, I'm kind of dumb when it comes to adding wires (I can only replace them) and I'd probably set something on fire

well you would need to do it correctly but yes directly from alternator output to battery for positive, there is a post on the back of the alternator, another would go for a ground from the alternator mounting bracket directly to the frame of the truck this may or may not help but I would think it would help.

 

[kbuskill]

I had a question about this. If something were causing the alternator to charge continually, would it be reflected on the voltage gauge on the dash? I.E. always above 14v?

If your gauge on the dash is working correctly then yes. And yes.

You mentioned an aftermarket tune.... what kind of tune is it and where did you get it?

 

[MichaelSE]

If your gauge on the dash is working correctly then yes. And yes.

You mentioned an aftermarket tune.... what kind of tune is it and where did you get it?

Got it, my voltage gauge works just as any other on any GMT900 truck I've driven. Typically higher than 14 at startup, drops below 14 while cruising. So it seems the variable rate system is working. My tune is a custom tune from BlackBear.

 

[kbuskill]

Got it, my voltage gauge works just as any other on any GMT900 truck I've driven. Typically higher than 14 at startup, drops below 14 while cruising. So it seems the variable rate system is working. My tune is a custom tune from BlackBear.

So does the whining stop or diminish when the gauge is reading lower? Or can you tell while driving?

Black bear is reputable so I would think that would rule out any mishaps on the tune BUT you never know, mistakes can and do happen sometimes.

 

[MichaelSE]

No, I haven't noticed it sounding different at different gauge readings. Turning on a ton of accessories or holding the window switches to close when the windows are already closed will change the pitch. Yeah, as soon as I find my OBD tuner (packed away in a box somewhere since I recently moved) I'll swap back to stock tune to rule that out.. or in.

 

[OptCodeVoid]

Hey,

If your still having this issue and you have ruled out all electrical possibilities I would check this video out...

Since you have a new alternator this could be you issue... just my $0.02 good luck.

 

[swathdiver]

A Tech2 would be nice to have in this situation to command the alternator to different outputs and check the noise and such. I was also thinking about a bearing problem and then saw Whys post.

Does the OP know that on the power cable coming off the battery is the sensor that helps regulate output and that often times the flickering lights is the result of this system working and that it can be simply disconnected for the alternator to put out full power all the time instead? My memory stinks, we just all talked about this in the last month or so on two different posts. ARGHH!!!!

 

[MichaelSE]

Thanks for the continued replies. I have considered belt alignment, but it is a distinct electrical whine. Not coming from a pulley or the belt. Swathdiver, I believe you're talking about the variable rate charging system. I've disconnected the sensor and there is no difference. Swapped back to stock tune, no difference. I'm just going to try my best to ignore it since I'm planning to trade in the truck soon. Then it will be the dealer's problem... it doesn't affect how it runs, just annoying as hell. I've put about 25k miles on it with the whine, still runs great, just drives me insane. But any other ideas are still appreciated.

 

[dubyagee01]

Alternator whine not related to bearings or the belt usually means the diodes are going bad.


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[mikez71]

I would try a third alternator !

 

[Doubeleive]

I would try a third alternator !

 

[mikez71]

2018? I dunno how that popped up.. now I wish I knew what happened.

 

[Doubeleive]

2018? I dunno how that popped up.. now I wish I knew what happened.

one thing you cannot trust is where a noise is coming from on these trucks "sometimes" I have sworn up and down before it was one thing and came to found out it was not.
a stethoscope is your friend. thought my alternator was making noise once and discovered it was the idler pulley instead, had no idea until I used a stethoscope and stuck it on there while it was spinning, taking the belt off didn't work because it was not under a load and couldn't spin it fast enough to tell. also thought my transmission was making noise once even using a stethoscope and turned out to be the rear differential, it was sending the noise thru the driveshaft. been a number of other times as well for different things