My 2000 996 c4 coupe's dome and door lights will pop on while driving... hit a bump and they go off. Also, many times I will notice hours after getting home that the lights inside the car will remain on. Can't seem to find the contact switch for the doors that activate the lights or track down a short in the wiring. Any ideas?

Brian

 

AFAIK, there is no contact switch for this at least like there is for other cars. Used to be a small plunger switch which the door closed when the door was closed or allowed to open when the door was open controlled the interior lights.

Nowadays this functionality is the inside the door latch switch and the door lock controller/security system.

In your car's case I believe the lights behave as they do because at least one door latch switch is bad and opens up and this signals a door is "open".

First check for any signs of dampness at the door bottoms. If there is dampness you have two problems. The dampness -- likely a door membrane is bad -- and the dampness has affected a switch. 'course, the switch can go bad even with no dampness. The switches just wear out over time.

A Porsche tech with a diagnostics computer can probably query the car's security system for any errors and probably confirm the door latch switch is the culprit.

There are DIY write ups on how to remove the door cover and remove/replace the suspected door latch switch.

The door lock has a fancy controller that can go bad but the behavior you report doesn't fit with this controller being bad. However that doesn't let that controller off the hook entirely.

 

Thanks Macster, I will dig into the passanger door handle this weekend.

Brian