factory A/C wiring
 

Hello everyone
I've been stalking this forum for years and love all of the information found here.
This is the first issue that I cannot find an answer to by searching.
Sorry if it has been covered before, but I cannot find what I need.
I have a 1987 toyota 4x4 22re pick up. I recently purchased an air conditioner out of another pickup. I got everything installed and working, however I had to splice the 4 wire plug from the evaporator to the 5 wire plug from the harness.
The unit does work but something is not right. The ac seems to lose its cooling ability after about 20 minutes or so. May be freezing up, not sure if auto a/c goes into defrost or not. also randomly when I turn off the ac it will blow the ignition fuse. Any input would be greatly appreciated.

I have installed AC, is it the factory AC? I have seen aftermarket AC in these trucks. If it is the factory AC, you may need to find the exact same year truck and get the correct AC wiring. I have seen a few differences.

Seeing you are a MO transplant, I am assuming you are here in Missouri. Nixa has a great salvage yard if you are in that area.

Is the compressor cycling or does it stay on the whole time the AC button is on? If it stays on your thermistor is probably not wired correctly.

As far as the wiring goes, the later model trucks use 2 wires for the thermistor and 2 more for the pressure switch. That is what is on the 4 wire connector. I am not sure what the 5th wire is on your harness. Do you remember what color it was?

Thank you for the responses.
yes, the compressor is on the whole time the button is engaged. If I remember correctly the extra wire from the truck harness is black. Let me give a little bit more info that might be helpful. In order to get the compressor to engage I had to put a jumper from the extra black wire to the black wire with a red stripe. not sure if this info is helpful or not . The A/c system is not after market. It came out of a 1986 pickup.

In general, AC systems have to have some method for limiting the on-time of the compressor to avoid freeze-up of the evaporator. Often that's done by sensing either the temperature or the pressure in the low side of the refrigerant cycle and cutting off the compressor if things get too cold. If that mechanism is bypassed, your evaporator will get below 32degF and ice up in humid conditions. When that happens airflow through the evaporator is blocked and you get no cooling, which describes your symptoms.

Thanks RJR
Thats what I was thinking. It seems like the evap it freezing. I can't seem to find any information on how to wire this system correctly. Does anyone have any info on the wiring?

You might want to get a subscription to Alldatadiy.com. They have accurate wiring diagrams.

Thanks Rustypigeon
I think I will try alldata. Hoping they have A/C wiring schematics
I will update with the outcome.

Any luck with this? I have installed the A/C system from a 1987 into a 1986 and am in the same situation except you are going from a 1986 to a 1987.

Having the same problem
 

How’s it. I have a 22re and having the same issue, replace entire ac system but my compressor just stays on and never cycles...did you figure it out?

Great info. Thanks