Alternator Noise

[Michaelpk3]

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?

[BobTurner]

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.

[tim2542]

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

[Michaelpk3]

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