My 1992 190e 2.3 has a problem with the wiper coming on intermittently with the switch in the off position. The first thing I did was replace the combination switch, which proved useless. So I figured the next step is to replace the wiper motor. Is there anything else I should check first before spending the $70 on a used motor? if not, is there a way to fix my current motor?

Further description:
The wipers will come on by themselves periodically, and will sometimes turn themselves off in a few seconds, and other times they are on for days at a time, in which case I remove the fuse. This problem occurs all the time, not just when it rains or when I wash my car....