# A tale of parasitic battery drain resolved!



## BIGmog (Mar 15, 2015)

Parasitic drain is a common enough topic I thought I would post on my own issue and how I resolved. Perhaps it will aid someone.

The battery would be dead after about 4 days of not driving. I had the battery tested at a local auto shop and there was no faults found.

I connected a multi-meter to the the negative battery cable and the negative battery post and found a draw of 450 milliamps. That's more than normal.

Next I opened the interior fuse box. I pulled each fuse out one by one and repeated the multi-meter test until the draw was reduced. The offending fuses were 15 & 38

Checking the service manual [smiley=book2.gif]

Fuse 15 runs Control module with indicator unit in instrument panel and also Transmission control module
Fuse 38 runs the Control module for central locking and the alarm horn

The cause was the infamous broken door microswitch. When the door is opened, the car starts up some components so it can be ready for ignition without delay. Because the microswitch was missing, the car can't detect if the door was opened or not. This caused the alarm system and the instrument panel to draw power constantly. :idea:

I replaced the microswitch in the door and confirmed it was working correctly. Still, the issue persisted.
What threw me off for a bit was that I had the door open while I was testing the fuses.

I closed the front door and ran the test again and now the draw was only a few milliamps.

Parasitic drain resolved!


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## Delta4 (Jun 19, 2015)

Top detective work, thanks for sharing 8)


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## rustyintegrale (Oct 1, 2006)

Where is this microswitch? I have a similar mystery drain on my roadster and the drivers door microswitch only works on occasion!

Thanks,

Rich


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## David C (Apr 15, 2013)

rustyintegrale said:


> Where is this microswitch?


In the lock in the door.


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## BIGmog (Mar 15, 2015)

Lots of details on the door micro-switch problem here

http://www.ttforum.co.uk/forum/viewtopic.php?f=2&t=181970&start=0

and here

http://audittmk1.blogspot.com/2009/04/door-sensor-fix-diy.html

once you find the right part, it's not an expensive repair.


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## Boruki (Mar 2, 2014)

Interesting to know.. Although I have battery drain on my siren rather than main battery.


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