My 2006 E320 CDI is experiencing wiper failure, whereby they stop in low, high, & intermittent settings (as well as fail to start) after having run for 15 minutes. Whichever scenario, shutting off & restarting the engine always corrects the problem, but only for a few minutes before they fail again. I can't find a relay. Legend has it there isn't one. Anyone have experience/insight with such nonsense?