Back the beginning of April I switched from heater to a/c and it popped the 10 amp fuse. It would pop any 10 inserted but briefly would not pop a 15 amp inserted for a short test period. Then it went to popping any fuse inserted like a direct short. I thought it was the coil and removed it and tested it which worked fine when hooked up to 12 volts on a bench. Once reassembled it would not pop fuses and for a few min it blew cold air then stopped. Still not blowing fuses it will not engage the compressor. The heater works fine but compressor will not run or blow cold. I can unplug the factory wire and put a jumper wire on it over to the batter and it runs the compressor and does blow cold. I want to find the issue and fix it properly not just wire in a switch, fuse, relay externally.

So what am I missing? What other electrical components am I not checking/testing?

Thanks

 

It's a mixed bag. Wish I could help.

My suggestion is taking a look at the a.c. lines for any refrigerant leaks. Low levels can present the issue you're having.

But the rabbit hole goes even deeper when it could involve restrictions in the system. You'd need some ac equipment to check high and low side pressures, and if replacing suspected components (including o-rings), evac and recharge the system properly.

If it were all electrical then hopefully tracing the wiring by the compressor, cooling fan, and switch for any shorts or circuits that give your multimeter voltages that shouldnt be present when the key is on and ac turned off. If you still run into fuses blowing. Seems it's no more of an issue?

 

The system has zero leaks and seems to only be an electrical issue. The fuse no longer blows and I have zero idea why it did and where the short was since I have not really changed anything. My questions is to someone that knows more details about this system such is there another relay to trigger the system hidden elsewhere other than the heater relay? When the coil is fed with a separate trigger wire the system runs as it should.

 

Toyota uses a AC Amplifier that is the computer for the AC system all the pressure switches and other goodies are controlled through that.

Put the Manifold gauges on see where you stand

 

There is a pressure switch that tells the AC system it can engage the compressor when sufficient pressure on Low side exists and you turn the ac on, you can test pressure switch by unplugging the plug going to the pressure switch and jumping the wires to test compressor clutch engagement, if it turns on the AC jumping it, you are low on r134a, typically these trucks leak at the evaporator under the dash, but regardless your best to add a can and see how it does by bring the pressure back up, if you have a leak it will stop working and you will have to have the system fixed, evacuated, replace the receiver dryer add PAG oil and hope for the best, if it is the evaporator replace the switching valve at the same time, easy job. Buy the gauges, they pay for themselves on 1 AC job and tell you how the system is working.

 

!. GET A SET OF GAUGES. You really are working blindfolded without them. And no one else can help you without knowing what they say.

2.RTFM. https://www.ether3al.com/runner96-02fsm/ac.html
Circuit diagrams are here: https://www.ether3al.com/runner96-02fsm/wiring.html

That's a good start.