I was experiencing a similar situation with my 89 300E. However mine didnt trip when it was wet. It would just cut out after about 10-15 minutes of use. Then, if I restarted the car the process would repeat itself. At first we tried replacing the belt as it was badly worn and likely slipping. However when that didnt eliviate the problem, my mechanic found that my A/C relay was at fault. About $250 later and Presto! Problem solve. That was last fall. Now its broken again. imagine that.