patzky1 Posted December 5, 2005 Share Posted December 5, 2005 Hi guys, I have a 77 and this winter my heater/defroster has not been working. I have already made sure all of the vacuum lines are in good shape, but only cold air comes out of the "panel vent" holes. This happens in vent, a/c, heat, defrost, etc. (every) position. Also, the heater control valve appears to be working because once up to speed I can feel some warm air coming out of the heat and defrost vents (depending on which is selected), but none while stationary. What should I be looking at to fix this? It seems like a door is not being switched, but which one? All I have is a Haynes manual and it's next to useless for this matter as its more geared toward 240's. Patsky Quote Link to comment Share on other sites More sharing options...
skipzoomie Posted December 6, 2005 Share Posted December 6, 2005 The piece you should check is called a mode door actuator. It's on the left side of the AC/heater unit. 3-4 inches in diameter. 2 vacuum hoses. Quote Link to comment Share on other sites More sharing options...
patzky1 Posted December 6, 2005 Author Share Posted December 6, 2005 Hey, thanks. I'll check that then and let ya know if that was the problem. Pat Quote Link to comment Share on other sites More sharing options...
patzky1 Posted December 14, 2005 Author Share Posted December 14, 2005 Ok, I feel like a dumb@$$ because I didn't try it earlier, but the mode door actuator was the problem. I just crawled under the dash while changing the heater/defroster controls and noticed the actuator diaphragm not being sucked in, so no defrost or warm heat. All it needed was a nudge the botom of the diaphragm to unstick it and now the system works like a charm. Pat Quote Link to comment Share on other sites More sharing options...
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