HELP! I have a 1982 300SD. The other night my defrost and heater were working fine, I stopped for a few hours and when I started it back up nothing works. The fan does not blow, the air conditioner does not kick on when the defrost button is pushed. It's like none of the buttons do anything. I checked the fuses and none look bad. What else could it be ??? I know I need to repair the mono valve, as the seals are bad, would that cause this?? Any help will be greatly appreciated, it's winter and I need the defrost & heat and the fan blowing. THANKS!!!