Speaker hum

Re-doing a CMC ..with the radio off ignition key to on position ( motor not started_)the door speakers have a pronounced hum in them again, radio is off, I haven't looked into it yet but...any ideas? Alan

First, suspect bad ground (or power cables run parallel to speaker cables) or bad amp in radio. Just cause the radio is "off" doesn't mean the electronics in it aren't powered on.

Check some other stuff too:

Eliminate outside interference. Does it do this if you're parked down the street?

Try pulling power from wiper motor and if equipped electric fuel pump. Those are the only other two things that could be causing EMF interference and the wiper motor would be unlikely. Bad relay (buzzing) could do it too, I suppose, but also unlikely. Might be easier just to pull all fuses except to the radio to check for these.

Pull the radio and 1 speaker and bench test straight off a battery. If there was no outside interference, and it's buzzing now, the radio's bad.

Justin mentioned likely causes. Most modern radios do more than receive AM/FM, so they may have a timed delay that keeps them powered for 5 minutes or so at startup and shutdown, to activate chimes, warnings, etc.

Check speaker ground, power cables too close to speaker wires, improperly mounted/loose antenna can cause gremlin noises also, as can localized rf interference from your shop/garage, etc.

Radios in our cars are comparatively inexpensive. If your Bimmer radio goes belly, you're looking at $2K to replace. How mad would that make you? It pisses me off, and I don't even own a BMW.

This could be caused by the antenna cable's shielding not being grounded..... Just a thought.

Thanks for the info, will let you know what I find later.

It could also be a crappy stereo.. After a 27-year career in automotive wiring, I'm a little defensive. I spent a lot of years wondering why they didn't design stereos to be used in cars, rather than designing cars to accomodate stereos. All of the above suggestions are good ones and may result in a quick fix. Pay particular attention to any line-level audio circuits that will be amplified, like between the head and a remote amp, or between multiple devices. Separate clean & dirty ground and power sources. Route clean circuits separately from dirty ones. Twist & shield wires, where necessary (I would recommend pre-made). You may have an amp that is powered up during key on and line-level audio circuits picking up the hum. That would point to shielding those circuits from EMI

...might be wave modulation...

Could be the radio forgot the words to the song.

Could be those hotwings you ate last night! :)

...or that 3-bean salad!

...or the cat you ran over that is still stuck under the car

.....leaky flux capacitor......

Duh! Source turned out to be a bad cordless drill charger.

Ah glad you found the problem .

I have been thinking of up grading my radio to a Koneg unit wit the extra mp3 port and a cd box on the side.

But they are so expencive to get one with a preamp built in. and I love my old cassetes. simmple easy to use and non desirable by radio theaves .
I have a big collection of casettes. Its a shame to have to update over 200 cassetes to a mp3s If that is even possible.

Any suggestions on what would be a best bang for your buck upgrade?