I have posted this problem a few weeks ago but did not have too much respons to it. Here it goes: Car= 1989 260E with only 246K.
Summer: A/C was cold and operating perfectly but at times, it would turn to full heat. A gentle tap on the gas pedal and it would turn back to cold.
Now the heater season is here (was 37deg. this morning). The heater works perfectly but for no reason will switch to cold A/C .
The switches (from hot to cold or cold to hot) seems to be vacuum related. It always switch at high vaccum (idle) and switch back to what it should be at low vacuum (acceleration).
Can anyone help? Thanks
JackD