The front passanger seat heater only work on low. The drivers side works just fine. Any thoughts? Would it be as simple as a bad switch or something more serious? How do I diagnose the problem?

Thanks!!

__________________
1973 280 - Sold
1980 300SD - Sold
1982 240D - Stolen
1988 300E - Sold
1989 260E - Sold
1989 560SEL
1994 E420 - Sold
1997 E420
2005 CL500