My Dad has a '94 Ranger with trouble in the AC system. It has plenty of R134a, but there is no voltage at the connectors of the Low or High Pressure switches, or at the AC clutch itself. The fuse under the dash is good, as is a fuse that is marked as A/C WOT -- I do no tknow what WOT means -- and the AC relay in the relay box clicks on and off.
The Owner's Manual states that the AC system will shut off in full throttle operations to send all of the available HP to the drive train instead of letting the AC system rob power. My working theory at this time is that the means of detecting full throttle operation as the AC system is concerned is falsely detecting full throttle. This would account for no power to the pressure switches or to the clutch.
I did a continuity check to the clutch and pressure switches, and all showed continuity. The Low Pressure Switch is located by the condensor (a large coffee can shaped cylinder) near the firewall on the passenger side. The High Pressure Switch is mounted to a hose coming out of the compressor, and the compressor itself is obvious.
The truck is also having an issue with the transmission that may be related -- if the transmissioin issue is electrical. My Dad reports shifting variations depending upon the truck being warmed up or cold. Perhaps the transmission trouble is really transmission trouble, I do not know and have not experienced the malfunction he thinks exists.
Back to the AC, how does the AC system know that the truck is in full throttle operation and shut itself off -- or how does the truck know it is in full throttle operation and disable the AC without affecting a host of other systems controlled by the Throttle Position Sensor? Except for the AC, and perhaps the transmission, there is no other reported problem.
The truck is OBD I, and I haven't a scan tool for it, but I'm not certain the scan tool would show this problem. The Check Engine light is not ON.