strange noises in a '87 Brougham

[JerRita]

a friend just got an '87 Brougham D'elegance and we got the A/C working but when the A/C is on the radio speakers hum? They're quiet when the A/C is off. Has anyone ever heard of this happening? Thanks JeRita

[James Landi]

Jerry,

I can't think of anything in the electronics of the system that would produce a radio frequency signal.  Perhaps the blower motor is the issue.  Is the radio interference on the AM radio?  The blower motors had a capacitor mounted on the outside of the blower casing that was intended to "quiet" the sparks that produce radio frequency "noise" that spin off of the carbon brushes on the blower motor commutator.  An easy way to check this is to simply unplug the blower and see if the radio interference goes away.  If the blower was replace at some point, someone may have left off the capacitor.  It's an easy "fix" if that's the problem  Hope this helps,  James

[TJ Hopland]

Blower motor and blower control module being located near the antenna also seems like there could be a connection there pun intended.  Maybe just clean up any grounds you can see in that area including the one for the antenna.  It may not have a ground wire but ground through its mounting that has corroded over the years.

[JerRita]

Thank you T J and James your replies put us on the right track. It wasn't the blower but someone had installed a new compressor and didn't replace the diode causing the radio interference Thanks again JeRita