It blows cold all day long at idle and parked. As soon as I pull a little rpm in first it goes hot. Will not go back to cold unless I pull over and turn off the engine, then it blows cold. Soon as I pull away in 1st it goes hot. The readings below were when the car was blowing hot or cold. Clutch was engaging without an issue.

Not sure where to start.

V-6 4.2L, 5 spd, 175k miles
Air gap on clutch is .025
Low side is between 20-45 (ac max, coldest temp, blower max)
High side 125-160 (ac max, coldest temp, blower max)

 

Low side and High side pressures are low. Probably needs a can of r134a. May have other problems too.

 

It is NOT an issue with the charge although the charge level may need to be addressed. Since we don't know what the ambient temperature was when those pressure readings were taken, we do not know if they're normal or not. If the temp was under 70F, they're ok. If it was 95 in the shade, the charge is probably low. However, the charge level will NOT cause your reported symptoms. Low side pressures are completely normal, indicating an operating cycling switch, although we don't know the rate of cycling. High side pressure is heavily affected by the temperature of the air through the condenser and we don't know what that was.

You need to identify if the outlet air temp, when the fault occurs, is actually going to ambient (plus a little) or is actually going to HOT. The first condition indicates the compressor has disengaged, the second indicates the heater temperature blend door is malfunctioning. The first condition is usually caused by a slipping AC clutch, the second by a busted blend door that's flopping around.

Good luck.

 

It was 90 f outside when I took those readings. The blend door seems to work. Driving to work this morning I used the defroster and other selections without using any of the Ac choices. I was able to adjust the temp from cold to hot. I would think if the door was bad I would not be able to do this? Also I don't here any flopping of the door. Not sure it you would or not. The clutch engages on the compressor when the failure happens seems to be about the same time interval as when it is blowing cold. I'm quite confused. I will add some Freon tonight. The high side readings do seem low for a 90 degree day I would think they would be above the 200 mark.

 

The AC is enable to operate in all climate control modes except OFF, VENT (PANEL), and FLOOR whether you realize it or not.

I would expect high side pressure in the 2.0 to 2.5x of the ambient temp (in °F). Quick check to see if it's in a logical range.

 

Fully charged on a hot day like that the low side could read as high as 45- 50 psig at idle speed and the high side 300 psig revved up. But don't believe me. Check on it.

 

I added another can of freon. It brought the high side to 230 psi but no cycling of compressor now. Outside temp 90 and humid. Its cool (not cold) but goes hot. If I turn it off and on at the control panel it will blow cool and goes to hot eventually. No compressor cycling, Pressure dropped on high side after a drive to 150, low side 25. On low side the evaporator/dryer is covered in frost and the connections going to it. High side gauge connector is very hot. Also the port on the evaporator is now leaking some green dye and freon.

What should I replace? Get one of the compressor kits from rock auto?

 

Why not take it to a pro who can properly diagnose it? In the long run it may be cheaper than shotgunning parts at it.