2000 Grand Marquis LE problem
 

I have a 2000 Grand Marquis LE.

It seems that when it rains the car tries to start itself when there is no key in the ignition. Eventually the battery gets drained and the car is dead and you have to jump it. The battery is not old. Has anyone had this problem or have any ideas on what the problem might be? Would really appreciate it.

I just got it a couple of months ago from my brother who was the sole owner. He has never had this problem with the car.