Alternator Noise

I recently changed out a 430W with a 650 and there seems to be a very strong alternator noise (much more than before). Same noise on com1 and com2. The ?whine? pitch changes with engine RPM. The noise goes away when I shut off the Alt Switch so this is telling me the alternator is the suspect. I currently have an Aircraft Spruce alt filter connected to the back of the alternator (60A plane power). P leads are grounded on both ends and I have ferrite core on the wire coming off alternator. Anything else to check? Possibly the alternator is going bad?

Lots of possibilities, but I?d bet you created a ground loop somehow. Is there an audio panel? Did you wire audio low (not ground) to the audio panel?s low input? Shields grounded only at audio panel? etc.

Is the battery still fully charged? Could be it?s low and with the alternator working harder a defect is exposed, like a bad diode maybe.
Tim Andres

It has a Garmin 340 audio panel. I'll have to check the low input.