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Battery Drain

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I am a Porsche neophyte. I purchased a 2003 Boxster with 2.7L and Tiptronic just over a year ago and love the car.  There are no modifications or accessories added to the car.  My battery dies if the car is left over night. The problem started last fall and I didn't deal with it before I put the car away for the winter. It's time to get it fixed.


I purchased a new battery that meets OEM specs last summer.  That battery is still good.  It charges fully, voltage after sitting for a day is 12.9 and it passes a load test.  The car starts fine and runs well with a charged battery, including multiple starts during the day.  If I leave it connected at the end of the day, the battery is dead in the morning.  The charger will not charge the battery if it remains connected to the car.  If I disconnect the battery, it charges fine.


I checked the power drain with the key out and after the car has sat for several hours.  There is a 4.6 A drain.  A mechanic friend suggested a bad relay so I pulled all fuses individually and the changes were minimal, less than .1 A.  When I connect the charged battery again, there is a clicking sound behind the spare.  I thought it might be the radio amplifier, but pulling the radio fuse didn't make a difference.


Any suggestions would be appreciated.

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Welcome to Renntech!


You can use a dc current clamp meter and clamp it on the alternator cable and see if the drain is from the diodes.




There are quite a few circuits that are not protected by the fuses under the driver's kick panel. If memory serves, ABS, airbag, immobilizer bypass that fuse box.

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