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Question

I have a BMW 740il and the onboard computer seems to be draining the battery overnight. is there a solution for this or is it a common issue?

Submitted: 1209 days and 22 hours ago.

Category: Car

Value: $9

Status: AWAITING CUSTOMER ACTION

Posted by JONATHAN 1209 days and 22 hours ago.

Info Request

WHAT YEAR IS YOUR CAR SIR?

1209 days and 20 hours ago.

Reply

Reply to JONATHAN's Post: the car is a 1993 with a V8 ( exact size I do not know)

Answer

I HAVE SEEN MANY DOCUMENTED CASES OF EARLY 90'S BMW BATTERY DRAIN ISSUES....THINGS YOU NEED TO LOOK FOR....RADIATOR FANS RUNNING WELL AFTER ENGNE SHUTDOWN...MISADJUSTED GLOVE BOX LIGHTS THAT STAY ON....TEMPERATURE CONTROL MODULE THAT STAY POWERED UP....DME (ENGINE CONTROL)UNITS THAT STAY POWERED UP...THE ONLY WAY TO ACCURATELY DIAGNOSE THESE CARS IS TO DO A PARASITIC DRAW TEST BY DISCONNECTING THE NEGATIVE BATTERY CABLE AND PUTTING AN AMMETER IN SERIES...VERIFYING THE DRAW...REMOVING FUSES AND RELAYS AND OBSERVING THE METER FOR CHANGE....IF YOU ARE ABLE TO OBSERVE AND CATCH SOMETHING STAYING ON IT WILL MAKE THINGS EASIER....THESE CARS ARE AMONG THE MOST DIFFICULT TO DIAGNOSE ELECTRICAL DRAINS BECAUSE OF THE COMPLEX WIRING AND MULTIPLE CONTROL MODULES AND NETWORKS....

Accepts:
Expert:	JONATHAN
Pos. Feedback:	100.0 %
Answered:	8/1/2006

JAGUAR/LAND ROVER SHOP FOREMAN

ASE CERTIFIED MASTER TECHNICIAN WITH L1 CERTIFICATION JAGUAR MASTER TECHNICIAN

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