does anyone know why my a/c compresure clutch stays ingaged. a/c works for about 5 min. then nothing but heat. the freon is fine. any help thanks jamie 1997 f-150 over 200000

 

replace compressor.
thats what im doing on mine tomorrow.

 

The "freon" is actually R134A, and how do you know it's "fine"?

You need to know what the system pressures are when it's operating. The symptoms you describe could be due to a low refrigerant charge and a bad clutch in/out pressure switch. (FYI: The clutch control pressure switch can be changed out without losing/discharging the refrigerant from the system. The switch mounts over a Schrader valve that cuts the flow when the switch is unscrewed from its mount.)

Put an AC guage set on the suction and pressure ports and see what the pressures are with max AC engaged, max cool, max blower speed and engine running at a fast idle. Discharge temps from the registers should be ~50 degrees, sometimes less if the system is OK...which it isn't obviously.

Suction or low-side pressure should cycle between ~27psi and~47psi. If the clutch won't disengage and the low side pressure is less than~27psi, the clutch control pressure switch is stuck closed. If the pressure won't pull down to ~27psi the system may be overcharged or the compressor is worn out.

High side pressure should be better than 180psi and runs typically around 220-250psi; a clogged orifice will run the pressure very high and will sometimes trip the high-pressure safety cutout switch (~420psi).

A good compressor should have a compression ratio better than 6:1, that is: With a low-side average of ~35psi, high-side pressure should be 210psi or more; however, high side pressure will vary widely dependent upon ambient temperatures with hotter temps giving higher pressures.