Our wagon is getting condensation on the inside which then turns into frost. Its no fun scraping both side of the windshield. Im guessing that there is a leak some where, or a loose seal, but I havent found it as of yet. We have 1995 e320 with about 120,000 on it and it runs just great other than that.

 

yup it sound like you got water inside somehow check the floor boards for dampness does it smell like mildewinside