2002 996 carrera with multiple electrical issues

I left my car with a dealer to sell on consignment. I took it back after two months, and while driving home found that the windows did not go up or down, and the interior lights didn't work. After I stopped driving it wouldn't restart. The mechanic at the dealer said to flip one of the light switches in the dome assembly near the rear-view mirror in order to start the engine--and that worked (wtf!). However, the windows don't go up or down, the remote key no longer works (light goes on), the hood and engine compartments won't open, and the window sensor that lowers the windows when you close it, is a little bit off. The convertible top goes up and down, and the windows raise and lower during that process. Another mechanic who looked at it told me it looked like someone had tried to break into the car through the convertible top, as there was some damage to the frame, but could that affect the electricals?? Any ideas?

Quotes source post: 9831562

Check for signs of dampness in the cabin, check the carpets and along bottom of the doors. A salesman could have left the top down during a rain storm, though I think there would be other signs of this. Another source would be blocked body water drains. Cars for sale get washed often and if a drain is blocked... Another possibility is the battery is near the end of its life. The car sat for 2 months. The engine was started I'm sure and the car moved about but the engine was not run long enough or hard enough to replenish the battery. I can't speak to the possible damage arising from a failed break in attempt other than if this was attempted the thief is stupid more so than the average thief. Jimmy the top open? Please. Slit the top, slither in, start the engine, lower the top, and drive the car away. (However, these cars are rather hard to 'hotwire' so unless the thief knows he can start the engine he's still stupid.) Later when the car is parked out of sight at some chop shop, the car is stripped and the damaged top canvas is trashed. Tops is relatively cheap. My money's on water getting in the car -- blocked drains -- or a weak battery. A thought is that the battery got weak enough that access to the car was denied and someone tried to get in the car by trying to jimmy the top until someone smarter stopped him. Sincerely, Macster.

Thank you for your response. It's quite possible that it got wet inside, considering there are flash thunderstorms all the time here in the Summer, but their mechanic said he checked all the relays and didn't find one that was bad. He also suspected the battery but told me it was OK. Maybe he missed something. Not sure if he used a scope on it, but probably would want to start there.

In the boxster the immobilizer is under the drivers seat, at the lowest point. (Not sure on a 996) When water gets into the cabin -- it settles there and can corrode the connections. you can remove the seat and see if there corrosion on any of the connectors or gnd screws. m

Quotes source post: 9831867

Any battery place should be able to check the battery for you free of charge. I get mine done at Pep Boys if you have them in your area. I know a normal battery will not even start these cars. I tried a fully charged battery from our Dodge caravan and it only just turned the engine over one time very slowly so you need a full charge on the correct battery for the car for things to work correctly. I have the convertible as well. Thats a simple job and a good place to start your fix.

A new battery will cost you less than an hour of diagnostic time at the dealer. Since all of your problems are electrical, I'd start there. Best of luck.

Thanks for all the advice. The mechanic at the dealer has the car now--they're offering to fix it, so I'll check to see if he's load testing the battery.

Quotes source post: 9831635

I concur