My Porsche 911 seems to have a battery leak or drain. Sometimes after only 3 days the car will not start. Is there anything obvious that I should look for?


Asked by Sep 05, 2013 at 03:55 PM about the 2003 Porsche 911 Carrera Targa

Question type: Maintenance & Repair

I have the car unlocked in my garage so
that the security system is turned off. Also,
as far as I can tell there are no lights on in
the interior of the car. The battery is only a
little over 1 year old and I believe the
alternator was about 2 years ago. AutoZone
said the starter and battery tested fine but
suggested there could be a leak.

10 Answers


A power leak could come from any electrical source including the alarm system even though you don't have it activated if the key is left in the ignition. If everything checks out okay (including the battery and the alternator), I would recommend using a "Battery Tender" device that could keep your battery at top charge level while it is just sitting there. Remember all batteries do discharge some as they sit for any length of time. If you have had an optional CD player installed or have heated seats, see if they are still using power while the car is "Engine Off, Key Out" of the ignition.

2 out of 2 people think this is helpful.

after you park take out negative terminal , when you put back and use again your car and it doesn't started again your battery is the problem, need to change.

2 out of 2 people think this is helpful.
Stephen Smith

Called a "parasitic" draw, it sounds like you've left something on. Make sure your hood is fully closed or the dome light shuts off, I know this sounds too simple, but this usually is the problem when a battery discharges this much and so fast.

1 out of 1 people think this is helpful.
Jason Reagan

Alternator will also drain the battery if it is going out.

1 out of 1 people think this is helpful.

Still having problems with the battery drain. I replaced the battery under warranty in September (3 months ago) but the problem is starting to happen again. It only takes about 3 days for the battery to drain enough so that the car won't start. The garage that replaced the battery also said the alternator and starter areally fine. The garage even attached a device that checked for any battery drain while the car was turned off and sitting show nothing unusual. They also removed the bulb in the trunk in case that was not shutting off. Is my only choice to keep the car on battery tender even if it's not driven for just one day?

2 out of 2 people think this is helpful.

Listen I wasn't working for a while and as such wasn't driving much. My battery was also going dead after a few days parked in the garage. My 2006 model I found out is prone to this and needed to be driven more or hooked up to a triple charger. I paid $125 for one at the dealership and have been worry free ever since. Well worth it in my opinion.

2 out of 2 people think this is helpful.
Best Answer
Stephen Smith

Try removing the bulb in the trunk on the drivers side. If that doesn't work, have your battery tested.

Andrew Dickens

3 possible causes - the front trunk light, the glove box light and the engine bay light. All are susceptible to micro-switch failure that defaults to 'light on permanently'. All of my 996's have had these fail. My current 996 had all 3 lights on permanently, the battery was going flat in 2 days. I replaced all the micro-switches and it has been fine since.

1 out of 1 people think this is helpful.
Jay Covington

It hasn't worked out for me yet. I bought my car new in 2008 and the problem was there from virtually the start. I keep the car on a maintenance plug-in device and it does maintain the charge. Good luck after you've started it for about the third time. I won't start. This is humiliating. You are in a 100,000 car and it won't start when everyone is looking? This is the PROMINENT fault in this vehicle as of yet unaddressed. My new battery is now on an actual charger. Do you leave it there? Unplug and switch to maintain on cigarette lighter? Seven years and still unresolved.

1 out of 1 people think this is helpful.
Stephen Smith

Bring it to a shop that works on Porsche race cars. Not a stealership. They have people who continuously sort out electrical problems, particularly parasitic drains, such as yours. You're right, you should not have to put up with it. Good luck!

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