1992 7.3L Diesel heat and A/C control problem
I have a '92 F350 7.3L diesel (non-turbo) that is having some problems with the heat and A/C controls. The fan speed switch works properly but the control knob that moves the output air from defrost to vent to floor does not work. No matter the position I move the control knob the only output is at the floor. I had the dash apart and I can see the colored vacuum lines (green, red, yellow, black and white) and there did not appear to be any breaks in any of the lines. There is also an electrical connection here but again I have no spec. My Chilton's guide does not give specs for the vaccum lines (meaning which one has vacuum for each output position). I am suspicious of the vacuum pump located on the engine as I also have very poor braking performance (the entire brake system is new including the hard lines). I see a large vacuum line running from the vacuum pump on the engine up to a valve that has outputs for the heat and A/C control but I do not have a spec for what the vacuum should be coming off the pump. Thanks for any help you can offer.