I have a 1997 F150, 4.2 liter. Two weeks ago the AC stopped working. The only thing I have noticed is the AC clutch will only engage for a couple of seconds then disengage for a couple, reengage for a couple and so on. I have checked the pressure and it is fine. No apprent leaks in the system. I have jumped the low pressure switch and the same thing happens. I have removed the blend door actuator and made sure the door is open for AC which it is. One of the tubes coming off dryer is very cold and drips condensation. Any ideas?

Is the clutch supposed to stay engaged the entire time the AC is on?

 

The A/C compressor has a normal on/off time, depending on the outside temp. It usually runs about 8-10 seconds on/the same off. If the condensor is cold, all the way down, but you get no cold air out the register, then either the orfice is plugged, which would raise your head pressure, or the blend door does not move into the a/c side, or there is not enough freon in the system. What are your head pressure readings, high and low side?

 

Where is the low pressure connector located ? I found the High side Right up on top.

 

The low side port is on the accumulator. Feel around for it, it may not be obvious.