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740 radio problems

My 1991 740 wagon radio isn't working properly. When it's on there's a terrible electronic noise coming from all speakers. The noise is worse when I operate anything electric (power windows or turn signals for example). It never gets better, only worse. Needless to say I don't operate the radio (except to see if miraculously the problem might have stopped).

During the winter the area that houses the antenna motor became full of water (drain plug was clogged). This is about the time the problem started, but I can't put my finger on it exactly. I replaced the antenna motor and the problem went away for about two months. Now the problem has returned.

Any ideas? I'm thinking a short in the wiring but I have never touched the wiring so don't know how that could have happened.

I posted a similar question when this first happened (about three months ago) and someone said there is a fuel relay that works double-duty as fuel relay/"something to do with the radio". Has anyone heard of this? I fos, where'w the fuel relay?

Thanks

Reply to
mgb
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Reply to
John Robertson

There is a radio noise supression relay in my '87 740. I believe the one in your car is located on the drivers side inner fender just in front of the shock/strut tower.

joe

Reply to
Joe

IIRC even the gurus say they can't define which models/years had the relay and which don't. My '85 765T doesn't. Ya never know until you look!

If I understand correctly, the presence of the relay suppresses ignition noise by changing where the power for the ignition is picked up. Don't quote me on that, and I hope somebody who actually knows will set me straight.

Mike

Reply to
Michael Pardee

Thanks everyone, Here's my latest update:

-Radio noise suppression relay. On my car it's on the passenger side, mounted on the rad overflow reservoir. I replaced that but it didn't cure the problem.

- bad earth problem. I was tracking down the bad earth suggestion at both ends of the antenna, and with the antenna unplugged from both ends the problem remained - so it wasn't that. Finally I noticed that when I unplugged the amp cable at the back of the radio, the noise problem disappeared. So, I accessed the amp, unplugged all the connections and plugged them back in - eureka! Problem solved - perhaps after all this time it was just a loose connection (knock on wood).

So far so good after two weeks.

Thanks to everyone for your help

MGB

Reply to
mgb

And thank you for the update. It will make it easier on "the next guy."

Reply to
Michael Pardee

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