I have a 2011 F-150. Recently it started blowing warm air and the cooling fan was extremely loud. Read somewhere that it was a bad expansion valve. I drained the system, replaced expansion valve, vacuumed system and recharged. The loud fan problem was fixed, but it’s still blowing warm air intermittently. Thought I’d replace the low pressure switch, but could only find one switch on a skinny line towards the front of the engine. No luck. It’s still blowing warm, then cold for a few minutes, then warm for a little while. That said, is there a low pressure AND a high pressure switch because I can only find one switch. Any help is appreciated!

 

you need to post the pressures on the low and high side while running.... and look at the CLUTCH to see if it is engaged a good portion of the time... normally when things get "HOT" for a minute its because the compressor has shut off ( clutch disengaged)... normally that means you are a little low on R134, but not always... You need to know the PRESSURE on the low side to see when it kicks IN and OUT. ............... how did you know how much refrigerant to install ?

 

Does your truck have the thermistor installed in the ductwork behind the glovebox?

https://www.ford-trucks.com/forums/1...blem-here.html
https://www.ford-trucks.com/forums/1...-solution.html

 

As another though, assuming the AC is working fine, if the blend door is broken and moving around the vent air temperature will vary.