I do have a tach signal that I use for my cruise control. I will connect it to the AC amplifier and see if that will allow the clutch to turn on and then go from there. Just knowing that the AC amplifier doesn't need the ECU to operate makes this much more simple. If I cant make that work I will get more and more aftermarket but I prefer to keep it as stock as possible. Thanks for the answers and the images. I have been struggling to figure out which wire is which from the wiring diagram. Actually seeing what the AC amplifier looks like is hugely helpful.
I think I mentioned I did have problems with pressures spiking as the daytime temps approached mid 90s. Even with the 4 runner factory condenser which has an additional condenser sitting in front of the main one, an upgrade from the pickups.
I went to a Pacific best Brand, not sure if the price now but has many more rows so it's much more efficient. I never had spikes register above about 275-280 after the upgrade.
I attached a wiring diagram on my other post from the 1st gen 4runner for the ac amp. the 2nd gen 4runner is a bit different mostly because it has a condenser fan along with a high pressure switch in the refrigerant tube to activate the high speed of the fan. The low speed fan is on anytime the AC is cycling. I included a pdf for what I have of the AC in my copy of the FSM
I've been working on this all morning and every time I think I figured something out I don't get the result I expected. I have a wiring diagram for my truck and I have identified all of the parts and junctions that I was looking for which feels like half the battle but I still haven't wrapped my head around how I should connect it all up. I want to use the factory system but what ever I'm doing doesn't seem to make it work. I'm probably missing something simple so I'll keep trying and hopefully dont wreck it further.
Several of the wires ran through part of the harness that I removed for the engine swap. I tried to keep everything that I would need and so far this is the first stuff that I wish I had kept. Hindsight's 2020. I found the wire that gets power when I turn on the AC so I am planning on running that through the pressure switch to a relay that runs both the condenser fan and the compressor and see what happens. If I have an icing problem then I will add a thermistor inline with the pressure switch to the relay. I figure as long as I have the pressure switches working I wont ruin anything.
There is a single pressure switch up by the condenser and a double pressure switch in by the evaporator. The wiring for the single switch is pretty straight forward and I think it was originally used to increase the condenser fan speed when the pressure was high. The double switch in by the evaporator is harder to figure out. It has four wires. I think two go to the lower pressure switch and two to a second high pressure switch used to cycle the compressor.
I'm very over my head with this so far but I'll figure it out eventually even if it would have been easier and cheaper to just buy another truck.
I think the four wires you are talking about are the thermistor and pressure switch inside the evap box as in first pic. yeah, the pressure switch up front is for high speed fan. I added another diagram for wiring.
I bought a hose splice to add a trinary switch and some other splices to better route the hose. I am just waiting on them to arrive. I should have all the parts in a couple of weeks. From talking to Coldhose I got the impression that using a thermistor was more necessary for R12 but R134a the temperature is better controlled by the pressure which is controlled by the volume and the trinary switch so I bought a switch that will cycle the clutch and the fan to keep the pressure in the correct range. If it starts to ice then I will look into putting a thermistor in the system.
Its been a while but I ended up buying a trinary switch and a ac hose crimper. I found a wire under the dash that comes on when the ac button is pushed and the blower is on. I ran that to the trinary switch and then to the ac compressor and the fan relay. It works great just in time for summer.
Sorry if I'm repeating myself but I didn't reread this thread.
