Looking for some insight on the operation of the heater control valve. My AC was giving me trouble by discharging 70 deg air max. Went through some posts & FAQs and checked my control cable. Sure enough the door was not closing all the way. Adjusted the cable and now get 55 deg discharge air on a 90 deg day (not bad for 1990 740 gle 107k miles.
Now I'm wondering about the heater control valve. It is vacuum operated but where does it get the vacuum from and in what position, what switch. I would tend to think it should not even be opened unless the temp control lever is off the left stop. As far as I know it is the original valve.
Any info would be appreciated.
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