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2010 S550 parasitic battery drain

3369 Views 3 Replies 2 Participants Last post by  kawagirl
Let it sit overnight and the battery will be completely dead in the morning. Battery load test is good. Alternator is charging very well (14V). Car will start right up after a good charge, but seems to have a parasitic draw and won't even light the gauges or chime when the door is opened after an overnight soak.

Where should I start looking?

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While performing power draw analysis with a multimeter there was a lot of continuous relay clicking going on in the front SAM and the current was fluctuating between 5 and 7 amps. Traced to relay C in the front SAM and also had some relay activity near the compressor for the suspension. Ended up disconnecting and reseating the electrical connectors to the ECU on top of the engine and on the compressor. Current draw last measured around 5 milliamps and the car has been good for two days now. Praying that a bad contact on one of those connectors was the problem.

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