its been doing it since i bought the truck back in '07 but then it was much more sporadic. you turn the truck on with the AC on and about the time the coolant temp is at full temp the climate control unit goes to full heat. moving the temp control sliders does nothing. the only way to get it to cool again is to shut the truck down. it happens much more often now than it used to. other than that stupid fault the ac seems to work just fine. anybody experienced this before and know what it is?

 

Mine does the same ****, its aggrevating..

 

Mine would do that when not moving when fans werent working... might want to check on those to make sure theyre moving a good cfm, that could be an issue.

Does it only happen at a stop at operating temp or does it even blow hot when moving?

 

The actual numbers on the climate control go to max heat or do they stay on the setting you selected and just blow hot air?

 

i had that problem a few days ago.. i changed the A/C compressor and now its perfect

 

If you have dual climate control and its blows hot on one side and cold on the other its gonna be your AC Actuator.

 

it's manual dual climate control with the 2 sliders but they don't have to be adjusted for the effect. it just does and when it does the sliders do nothing; it's at full heat from all vents. this happens under the same condition every time: minutes after initial start-up (cold or hot) but only once the truck has reached operating temp. until then it blows cold. if the truck is already warm it begins seconds after start-up but still after blowing cold. its not the compressor because it only does this some of the time and cools fine at a stop or driving when working like it should. but when it's acting up it's not just not cooling: it's blowing FULL HEAT... like the burn the hair off your knuckles kind of hot. seems to me to be a control issue instead of mechanical one for these reasons and that it only requires the truck to be shut down for seconds before restarting for it to work normally again.

 

The air doors to the heater case are most likely stuck or the foam seals have worn off. You can always do a heater core bypass valve and keep the heat off in the summer.