Alternator Isolated ground 12 side?

[Abbylind]

I know the passenger side alternator has an isolated ground for the 24 volt side of the system. There is a phenolic insulator on the (-) ground lead on the alternator. I looked at the drivers side alternator and it has the same phenolic insulator. Ive got a wicked alternator whine on the 12 volt side. I installed a external capacitor on the drivers side alternator...still no joy. Could I have a ground loop problem with the drivers side alternator?..... Thoughts?

 

[richingalveston]

I would think it possibly in the alternator it is pretty cheap and easy to rebuild so before chasing the moon I might start with that. The entire truck in essence is a ground loop by design.
Does the noise change with load. Can you switch the heater fan speeds and change the sound?
I assume the whine you are talking about is coming out of your stereo speakers?

Just trying to get more info to help

 

[Abbylind]

Good questions! Yes the whine changes with engine RPM. I can hear it through my two way radio and my stereo...when it worked. I was installing a capacitor on the back side of the alt when I noticed the insulator on the back side on the ground lead. Im wondering in my 1008 had a isolated ground alt installed on the drivers side at some time....

 

[Abbylind]

Can someone post a pic of the back side of the drivers side alt? Id like to see if there is the same insulator....?

 

[Tow4]

Both alternators are isolated ground originally. Only the passenger side needs to be isolated ground.

 

[Abbylind]

I guess I can try grounding the negative alt terminal to the frame and see if the whine goes away....
Anyone see a problem with that?

 

[NovacaineFix]

If adding a capacitor to it doesn't stop the whining then it could be a bad diode in the diode trio inside the alternator, hopefully not.

The diodes changes the AC into DC but if you're hearing radio noise like the whining you stated, it may be one or more of the diodes breaking down allowing partial AC flow through causing the noise.

Also check your grounds and make sure that you have enough that are in good shape and properly grounded. Loose, bad grounds or not enough grounds can sometimes create that whine, but I would suspect the alternator 1st.

Let us know what you find.

 

[Abbylind]

Rebuilt drivers alternator at first the whine was still there. After a time of running the engine the whine went away....

 

[NovacaineFix]

Maybe just buy a louder radio, that always drowns out those pesky whiny noises, lol