Yesterday, after I left the car wash, the electrical system in my car went haywire and I couldn't start the engine (indicator lights all on, tank gauge low while car was filled up, radio kept playing after removing keys,...). We jumped the car and it ran fine for a day, everything recovered. This morning, similar issue. Jumped it again and it ran fine. Could it be that the battery is just coming to end of life and is that causing these electrical issues? Coincidence it happened after car wash?

The battery is the original one (2010 Cayman S) and I am driving the car daily. Thanks!

 

While it could just be a coincidence and the battery is going out -- or the battery is ok but the alternator is not putting out enough juice -- I suspect what happened is a body water drain is blocked and water got into the cabin or if not the cabin proper flowed into someplace it should not have flowed into.

Check the body drains.

Check for dampness of the carpets, under the seats, especially the passenger seat, at the bottom of the doors and the rear trunk towards the back bulkhead where the DME is located. While you are in the mood you might as well check the front trunk for any signs of dampness as well.