I'm new to this site today so any pointers on how it works or something I need to do please let me know.
I have a 1990 300TE with 135k miles.
I just started having heater problems. It works fine as long as I'm moving above 10 MPH. When I stop the heater blows cold air. As soon as I speed up it starts working again. It seems like a vacuum leak? Is there a servo that controls the heater? Any help would be greatly appreciated.