A/c Sometimes Fails To Change From Hot To Cold ?

[TXD]

on my '01 2500hd i try to change the temp control from heat to cold a/c and it will not change unless i flip knobs back and forth and flip it on and off. inside air, outside air, vents toward floor, passengers, defrost, a/c button on or off it dont matter. i have to mess with all of them then all of a sudden it seems to finally "flip" over and have cold air. anyone had this happen and have an idea for me to look into?

[98silvz71]

on my '01 2500hd i try to change the temp control from heat to cold a/c and it will not change unless i flip knobs back and forth and flip it on and off. inside air, outside air, vents toward floor, passengers, defrost, a/c button on or off it dont matter. i have to mess with all of them then all of a sudden it seems to finally "flip" over and have cold air. anyone had this happen and have an idea for me to look into?

 

In the summer when I am running the a/c sometimes I will get only heat. It has to do with the mixing valve popping open and dumping the hot coolant through the heater core. It is a rather difficult part to get to if you don't want to tear the dash apart. So I have to shut the engine off to release the pressure and then it will work fine. I am not sure if this is what you are having problems with. Maybe when I can afford it I will replace it.

[steiny93]

a couple vehicles ago the wife's 2000 yukon did the exact same thing

'i believe' it was the switch in the dash that was a problem, I'm pretty sure it was that but I can't recall 100%

if you know someone with the GM Esi have them get you the trouble shooting steps, for the yukon it was a no brainer

 

i also remember that if i wanted to make it work i could disconnect the battery and reconnect then all would be good for a while