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What car.
My top 3 guesses:
- do you have one of those BT diagnosistc readers plugged in?
- Sun roof
- tow bar
- do you have one of those BT diagnosistc readers plugged in?
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Found mine using a multimeter (measuring voltage, wired between neg and battery) and pulling fuses until I found the circuit. I then had to work through the manufacturer wiring diagram to find the culprit. Worth it in the end
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An old poorly fitted immobiliser or alarm is my guess. Or if it's an import, terrible wiring on the rear fog light is another possibility.
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The last thing you test or the one possibility you forgot....
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Best way is to disconnect the positive terminal on the battery, put a multimeter between the terminal and the battery post, with the multimeter set to measure amps/current - if you have it to set something else the chances are you'll fry the multimeter. That'll tell you the parasitic current draw. Then pull fuses one by one until you find the one which makes the number drop to zero or almost zero. That'll narrow down which circuit is causing the problems.
You can measure voltage instead, but current is better.
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@root
Is there and idiots guide anywhere to finding what is draining my battery while the car is off? I installed a new one as I though the old one might just be buggered. A couple of days later and its dropped about 0.5V