alternator whistle at idle

[crispyboy]

Over the past few days the alternator in the truck has started a whistling sound when the truck is at idle. It seems to go away when the rpm reaches 1000+/-.

I don't like annoying odd noises.

Any ideas?

Would an alternator rebuild shop be able to diagnose this noise?

 

[RCorbeil]

Yes... ... . Must likely a diode is toast.



Ron

 

[K5IP]

Whistling noises are usually mechanical. Probably brushes.

Rog

 

[rbattelle]

Could also be a bearing going out.

Anyway, any reputable alternator rebuild shop should be able to diagnose and repair it.

-Ryan

 

[ABennin]

My A/C clutch bearing started to go and would make noise at idle and go away above 1000 rpms until it gave out. I would have sworen it was the alternator except that it was only 4 months old. I did send the alternator in and they said everything was fine with it and I put it back in. I took it to the only place where I have the truck serviced and asked him. He thought it was the alternator too, but we had ruled it out. So next was the belt tensioner, still did it. Pulled the A/C clutch next, and it was bad bearing.

 

[crispyboy]

Update:
I took the truck by the shop who specialized in alternators and both of us concluded that it likely was not the alternator.
I took the truck home and checked all the hoses and clamps etc on the air intake system up to the turbo. The only odd thing I found was the foam around the intake silencer was drenched in oil. I cleaned up the foam, reassembled and have not heard the noise again. Got my fingers crossed on this one... ... .