Wipers and lights go on randomly

I found the owner of a 2000 Jetta TDI (140k miles) at work that is having strange problems. She has been to Colonial VW in Massachusetts numerous times for electrical issues. While driving her lights sometimes don't come on, or the wipers go randomly. The dealer has replaced the computer, the ignition and looked at it numerous times. Most recently they had the car from Monday till Wednesday and declared it fixed. When my friend drove the car home everything was fine until she turned it off. That's when the lights came on and the wipers started going.

Can anyone think of a reason for this odd behavior? Or have any idea of what to do with the car?

Thanks!

Coolant migration.