On my 1982 300sd I can't get the vent to move to the heat position, only defrost, a bit of searching hasn't turned up any obvious culprits and I don't want to jump in blind, can anyone give me some pointers here? Is this vacuum operated?
welcome to my world, i just had the same problem with my '85sd. there are various things that can cause this, most likely a vacuum leak. from one of your vacuum actuators, switchover valves, or vacuum lines.mine was a bad actuator for the center vents leaking. i disconnected it plugged the line and all the other functions worked properly. you'll need a vacuum pump to check them with. i'll check back with you later gotta go to work!
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