Truck Cab Air Con Pump connection

[Lee & Joan]

I have an 86 Toyota 4 cyl 24 RE engine with air conditioning. It was retrofitted to the new freon & has a new pump. The Truck Cab AC does not work & while checking its fluid status it was noted that the hot wire for the pump magnetic clutch was not connected to anything. This is controlled by the A/C Amplifier under the dash in the cab heating cooling unit. Assuming the wire would connect somewhere in the wiring harness on the passenger side, I spent sometime under the engine where that harness snakes into the area under the intake manifold, and even pulled the front part of the harness off the front injector and several sensors under the front of the manifold, but found no wiring connector for the A/C pump magnetic clutch. If I hot wire that clutch wire to 12 volts the compressor pump engages. However there are a number of sensors in the A/C system to over ride the clutch if something goes wrong, so hot wiring around the system is not a good idea. I looked at a 1991 Toyota with A/C and there was an AC mag Clutch wire coming off the front section of the passenger side engine harness, but this 1986 does not have that wire. Does anybody know where that pump wire is routed ?

[Bob C]

On my '88 Escaper, tracing the wire from the compressor backwards it goes first to the pressure switch on the dryer/accumulator tank. The pressure switch is wired to a wire harness that goes into the firewall on the passenger side right next to the hood hinge.

The problem with my A/C is that I get low voltage to the pressure switch through this harness. I am assuming a bad relay or switch somewhere in the system. The schematic shows the relay but does not give me a location. I assume that the switch they show is the one on the dash marked A/C (really bright I am.) Can someone help out this the location of the relay?

[Lee & Joan]

I went back under the dash behind the glove box and found the 8 pin connector to the "A/C Amplifier" that sits on the top of the cab air conditioner. Then I found the black with red stripe wire tapped into it and tested. Engine ON, no volts, AC button ON no volts, Fan on volts. All three have to be on for volts, if any are off you should get no volts. I sent this wire then through the firewall grommet, and hooked it into the compreesor wire, and away she goes.

Bob, there is a relay for the heater circuit (also does cooling) in the heater fuse area. Also shows one behind glove box by the AC unit. Looks like the heater fuse is on the passenger side of the center consul (stereo area) accessed by removing glove box.

[Bob C]

I understand the engine on & heater fan on & /c switch on requirement. My problem is that the voltage at the accumulator tank pressure switch is about 11.5 volts and that is not enough to engage the compressor clutch. What exactly is an "A/C AMPLIFIER"? What exactly should the voltage be when you test it at the pressure switch? I have jumped from the battery to the switch and everything engages.

I have a relay that will trigger at 11.5 volts and was thinking about putting this next to the pressure switch to use the engine/heaters/ac circuit with direct battery power triggering the clutch (with an inline fuse of course.) I would love to actually be able to just repair the problem of course but I am semi-stupid about where the switches are or what an a/c amplifier is. I know the physical location of the ignition, heaters, and a/c switch but was lost as to the location of the a/c relay. I will be following the circuit in the near future and look behind the glove box for the a/c relay.

Am I correct in thinking that my problem is actually just a bad connection somewhere?