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2010 S550 parasitic battery drain

3370 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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Get an Amp clamp, open your hood and place it around the negative cable leading into your batter (make sure it is pointing in the right direction, the clamp should have an arrow showing the “flow” of electrons). Keep the hood open, close both hood latches, close and lock your car and let it sit for about 30-40 min. When you first lock the car, you will see your Amps around 6 A or so, then as your car “goes to sleep” you will see the Amps drop as everything shits down. After about 40 min, you should be able to see if you have any draw on your battery. There should only be about .5A when the car is asleep. If you have more than that, go to your fuse box and start unplugging fuses one at a time, when the Amps drop, that fuse is the area when you something is staying on. If you have WIS, you can go into the wiring diagram and see what the fuse is attached to. This will at least narrow down where the draw is coming from.
Way to go! Let’s hope it is fixed!
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