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dkwl93

E30 Parasitic Drain - Fuse #21, #24, #28

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Hey all,

I've recently purchased a 1990 BMW E30 325i (South African) and have an issue with parasitic drain on the battery.

I drove the car daily since purchase (~1 week) and it has been starting great each time. However, I didn't drive it for 1 day and found the battery was dead the next day. I then jumped the car and drove around for a while (~20 mins) and found the battery had a charge of > 13V when the engine was on. 

I then unhooked the battery, closed all doors and put a multimeter in series with the ground of the battery (Multimeter at 10A) and pulled out all the fuses where I got a current of 0.02A. I then started to put in all the fuses 1 by 1 and noticed at Fuse #21 the current would go up to 1.8A. This seems ridiculously high. I kept going and found fuse #24 and #28 also increased the draw by a noticeable amount (~0.1A each).

My question is what could be the possible cause of this parasitic battery drain and what should my next steps be?

Other things to note is that there is an aftermarket alarm and aftermarket stereo installed. Also, the antenna gives me radio but seems to be stuck around halfway.

I did some research and found that my symptoms were exactly the same as this person: 

Any help would be very appreciated.

Thank you!

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Thanks for the help. I unplugged it but still have the same draw. It's not the problem. 

On an unrelated note, is it safe to drive around the car without fuses #21, #24, #28

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Your next step would be to see if all of your interior lights actually turn off when they are supposed to. Otherwise check your aftermarket head unit wiring. You should be fine without fuse 21 and 28. 

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I'll give these a check tomorrow. Also, could the aftermarket alarm be connected to fuse 21? 

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Most likely, if your indicators flash when you lock/unlock your car. 

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E30s have unloader relays that can fail, from memory the K7 or K9 relay(s).

They control a group of fuses and put the circuits to sleep after a short period or when not in use.

Do the same test with your meter but pull those relays instead of the fuses.

 

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Update - I'm starting to think theres a short somewhere in my wiring. My reasoning for this is is that Fuse 28 controls the cigarette lighter and the Aerial. I've unplugged both these components and put the fuse back in and found that the battery is still drawing 500mA compared to ~50mA when fuse 28 is disconnected. 

I'm thinking that this might be too complicated for me to diagnose. Does anyone know any good e30 electricians in the Auckland (preferably North Shore) area? 

Thanks so much for all your help so far

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On 4/1/2017 at 5:29 PM, dkwl93 said:

Update - I'm starting to think theres a short somewhere in my wiring. My reasoning for this is is that Fuse 28 controls the cigarette lighter and the Aerial. I've unplugged both these components and put the fuse back in and found that the battery is still drawing 500mA compared to ~50mA when fuse 28 is disconnected. 

I'm thinking that this might be too complicated for me to diagnose. Does anyone know any good e30 electricians in the Auckland (preferably North Shore) area? 

Thanks so much for all your help so far

Hey, you ever figure out what it was? I've got the same issue with mine. Bloody headache! 

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