I installed a new monovalve the night before last and my heater worked great, temp stabilized etc. The next day I could only get action out the entire climate control system by turning the temp wheel to the extreme cold setting and the fan switch to high. Any adjustment of the temperature wheel to a warmer setting or hitting the defrost button immediately stops the fan. Only by setting it back to the extreme cold setting and using any button other than defrost will it come on again, and only on high. Any ideas as to what's going on? I'm new to Mercedes but love my '83 300SD. I'm sure that once I figure out how everything works in it I'll love it even more, but for right now it's snowing and verrrrrrrrrry cold in the Benz.........