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Help With A Electrical Problem...

Jon Burson

By Jon Burson,
in BMW 7 Series Forum

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Jon Burson Apprentice

Jon Burson

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I have a 1994 740iL with a 4.0 V8. I have a moderate battery drain as long as fuse number 20 is plugged in. When the car is off, I hear a somewhat quiet electrical noise under the cowl on the firewall underneath the dashboard. I need to figure this out. Please reply with some input, thank you.

Guest DazH

Guest DazH

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I have a 1994 740iL with a 4.0 V8. I have a moderate battery drain as long as fuse number 20 is plugged in. When the car is off, I hear a somewhat quiet electrical noise under the cowl on the firewall underneath the dashboard. I need to figure this out. Please reply with some input, thank you.

Firstly, welcome to our community =]

Fuse n0# 20 is linked to the rear windscreen heater and the climate control (AirCon).

Is the electronic noise you hear the same as when you turn the blowers to "0" ?

Daz

Jon Burson Apprentice

Jon Burson

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First off, I came to the belief that there is in fact 2 problems with my new 740iL. 1 is most likely the infamous "sword" resister. Because after hours of research I found that the cause to my blower only operating at full speed was the "sword". This has yet to be replaced. 2 is the one I first mentioned to start the topic. All I can say is that there is some electcial noise that is emmiting from somewhere behind the radio. Still not sure what is causing my battery drain though. But I'm very confident that this battery drain is most likely caused by the Anti-Theft System.

Guest Mister Dabsy

Guest Mister Dabsy

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Yes I know it well... It is the climate control (had the same slight buzz/hum in my 7series)... Change the hedgehog resister anyway, pull the climate unit out and check connections. Car battery needs to be a good bugger on yours too !!

Jon Burson Apprentice

Jon Burson

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so I just finished tearing her apart. I'm not sure why but the battery drain and noise all dissapeared as soon as unplugged the A/C Control Module. I plan to replace both the module and the "sword". Anyone know where I can go to replace these with really reliable parts at a reasonable price?

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