Got a 2002 blazer 4x4 4.3 alternator whine cant figure it out .i know sounds so simple .. I changed alternator 3 time got a new belt tentioner. Belt. idler pulley a.c. new power steering pump and it still whine it seems like it only does it at 500 to 1000 rpm cant really hear it after 1000rpms and sometime itxdnt whine at all i need help im tred of his god awful whine

 

First, how do You know this is alternator?
Second, is there a chance You have some oil residues on a serpentine belt surface? I.e. from leaking oil
Third, if alternator is whining, it will most probably be slipping. Observe the battery gauge once You start the engine. Does it build a voltage on idle fairly quick (under 5s)? Or the 14V voltage is built over 1k rpm?
Fourth, what's the position of Your tensioner? It has sort of an indicator for a serpentine belt wear.

 

Are you sure you have three whinning alternators in a row?

You can narrow down the source of the noise with an engine stethoscope. I use a tire iron held on one end in a fist against my ear. Be careful with all that stuff spinning around. Touch the other end to the various suspects until you find the problem.



George

 

Its the alternatir if I un plug it it stops or take belt off it stops

 

Yes 3 if inunhook it it stops whinning or if take belt off

 

If You take off the belt, You disable:
- tensioner pulley
- steering pump
- AC compressor
- water pump with visco/fan clutch
- alternator
- idler
so I wouldn't point at the alternator that quickly...
If You remove the belt, do You feel any play of the alternator shaft? Does it run freely? I renew the question on the tensioner indicator and the other questions above as well...

 

So it stops whinning if you leave the belt on but unplug the electrical connections?

Are all three alternators the same brand and new/rebuilt?

George

 

Yea it stops when unplug it. No that's where diffrent and had them checked at autozone

 

By unplugging the alt you relive the drag load and vibrations it creates on the belt drive system as it charges - Gonna sound stupid but check the fan clutch - I've seen it happen ......

 

Do they heat up abnormally when You plug them in?