1989 m3 e36 battery drain over 4 days

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   Help!...
I have a M3 that seem's to drain the battery every 4/5 days, its a new battery as the previous one did the same.

I have read it may be a heater fan pack, the car has the full air-con system install, the fan works fine off to full speed I believe the control head was changed a while ago for other issues?.

I have had the car 1 year, most of the time its been in a garage as the fault means I can't leave it between drives with out the battery going flat.

Is there any way of determine the issue.

Thanks

Ian

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Ianhm Members Profile Send Private Message Find Members Posts Add to Buddy List Forum Member Joined: 23 Jun 2016 Location: Kent Status: Offline Points: 3	Post Options Post Reply Quote Ianhm Report Post Thanks(0) Quote Reply Topic: 1989 m3 e36 battery drain over 4 days Posted: 23 Jun 2016 at 5:33pm
	Help!... I have a M3 that seem's to drain the battery every 4/5 days, its a new battery as the previous one did the same. I have read it may be a heater fan pack, the car has the full air-con system install, the fan works fine off to full speed I believe the control head was changed a while ago for other issues?. I have had the car 1 year, most of the time its been in a garage as the fault means I can't leave it between drives with out the battery going flat. Is there any way of determine the issue. Thanks Ian

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dteagles Members Profile Send Private Message Find Members Posts Add to Buddy List Club Member Joined: 09 May 2007 Location: UK, Bucks Status: Offline Points: 3476	Post Options Post Reply Quote dteagles Report Post Thanks(0) Quote Reply Posted: 23 Jun 2016 at 5:40pm
	You need to disconnect the battery and put a meter (measuring current) between the battery terminal and fhe cable and see what the current drain is. If you have a lot of current flowing with the car locked and nothing working I would suspect the alarm but you'll need to try and disconnect things individually (fueses are probably the easiest way) until you spot the one that's causing the drain.
	Think about what you can do for the club, not what it can do for you...

Mike Fishwick Members Profile Send Private Message Find Members Posts Add to Buddy List Forum Member Joined: 04 Aug 2006 Location: France Status: Offline Points: 2753	Post Options Post Reply Quote Mike Fishwick Report Post Thanks(0) Quote Reply Posted: 25 Jun 2016 at 1:57pm
	If you do not find a fuse which cuts the discharge back to its normal 30 mA or so, try disconnecting the alternator and the starter motor, both of which are directly connected to the battery. The problem may be due to a short-circuited diode in the alternator, or a build-up of copper debris inside the starter motor contactor. Tackle this work logically, and write down what you have done - memory can play tricks on you! Edited by Mike Fishwick - 25 Jun 2016 at 2:04pm
	A Z3 is not just for Christmas - it's for life!

Ianhm Members Profile Send Private Message Find Members Posts Add to Buddy List Forum Member Joined: 23 Jun 2016 Location: Kent Status: Offline Points: 3	Post Options Post Reply Quote Ianhm Report Post Thanks(0) Quote Reply Posted: 25 Jun 2016 at 5:50pm
	Many thanks for the ideas. I am out over this week end I will post the outcome next week.

MICK Members Profile Send Private Message Find Members Posts Add to Buddy List Club Member Joined: 29 Mar 2007 Location: United Kingdom Status: Offline Points: 181	Post Options Post Reply Quote MICK Report Post Thanks(0) Quote Reply Posted: 06 Jul 2016 at 11:43pm
	Had a fault on a car similar to this in the past. Disconnecting the battery and measuring current drain with an ammeter was inconclusive so the battery was reconnected and if the car was not used ,the battery would maintain it's charge,but once used ,the fault would return. The fault was found to be a relay in the ECU staying operated and draining the battery. Disconnecting and reconnecting the battery released the relay ( temporarily clearing the fault ) which stayed released until the ignition was switched on again when it would operate but stay operated even when the ignition was switched off thus draining the battery again. An auto-electrician remedied it but fitting an external relay, the contacts of this relay were connected into the wire which supplied the voltage to the ECU. When the ignition was switched off , this relay released and interrupted the supply to the ECU which released the offending relay in the ECU. It lasted until the car was sold about 5 years later.