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Battery Problem

roadrunner Jan 21, 2010

  1. roadrunner

    roadrunner Member

    Have a problem on our A3 2000 1.8 which is driving us loopy.

    Battery slow discharges. But its intermittent so when not in use for a few days its dead. The battery (1 year old) tests Ok and the alternator is charging ok but something is draining it.

    Anyone had a similar problem and can offer any suggestions.

  2. aragorn

    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

    Ok, get yourself a multimeter that measures amps, and some decent clips. Remove the neutral battery lead, and connect the meter between the battery and the lead, so your completing the circuit thru the meter. Make sure the circuit isnt touching anything metal.

    DO NOT attempt to start the car when its like this, and keep the ignition off while testing. Turning the ignition on and powering up all the associated circuits could easily fry the meter.

    Have a look at the reading. It really should only be drawing a few tens of miliamps maybe upto 100ma or so, but if its killing it that quickly i'd imagine its more like 0.5-1A draw.
    Now get someone to watch the reading, and start pulling fuses, and see if anything makes the reading drop. If not you need to then look at components that are powered all the time, like the central locking/central convenience module, engine ecu, and even the alternator itself.

    Can even be something as simple as the boot light is staying on.

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