Factory Radio Alternator Whine

[Kable]

Factory radio has the annoying whine. Goes up and down with RPMs. I checked most the grounds on the battery and all seem to be good. All factory wiring and speakers.
Any Suggestions?

 

[1low95GMC]

im having this problem with a aftermarket radio too. some one help

 

[MIHELA]

Bad diode in the alternator can cause that, it's fairly common. Check for AC voltage with a multimeter between battery and ground. Shouldn't be much.