The a c servo is not working on my 1980 300d. The lines to the servo are hot but the lines leaving to the heater are all cold. A new on is far to much for me. I've checked the yards and couldn't find one. Is there a kit out there to rebuild one. Is it very complicated once you've opened one up. Perhaps someone knows of a DIYS tutorial i can link to. Is there a part of it that fails more often than the rest. Are there any places they sell them cheap. My car is a keeper, I would just like HEAT. Thanks RAY M