How to install A/C in a 1st Gen Pickup/4Runner (1 Viewer)

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Great write up man! The only thing I will mention is that you want your TXV bulb directly against your suction line
(no insulators) the TXV (expansion valve) needs to read the true temp of that suction line in order to accurately meter refrigerant into the evaporator coil. The heat shrink will slightly skewer the effectiveness and efficiency of your system. I wouldn’t worry about it now but for anyone in the future. I think if you wrap it tight enough you shouldn’t have a concern about a rub through.
 
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Im using my 86 4runners factory ac system with a VW engine. My factory wiring harness is shot so I'm doing wiring wiring from scratch. I intend to run my AC off a 30 amp relay. I have a question on wiring in the low pressue cut off, is the low pressue cut off a normally open or normally closed switch? Also is it designed to have ground or 12v go through it? Im not sure if i need it to feed a ground to my relay or the the 12v "on switch" to my relay?
 
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Im using my 86 4runners factory ac system with a VW engine. My factory wiring harness is shot so I'm doing wiring wiring from scratch. I intend to run my AC off a 30 amp relay. I have a question on wiring in the low pressure cut off, is the low pressure cut off a normally open or normally closed switch? Also is it designed to have ground or 12v go through it? Im not sure if i need it to feed a ground to my relay or the the 12v "on switch" to my relay?

I would think you will still need the AC amplifier to control the system which is what the low pressure switch is wired to.

To answer your question. The low pressure switch is normally closed when the system is charged with refrigerant. It appears to have 12v going through it once the AC button is pressed.


ac wiring.png
 
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What exactly does the amplifier do? The reason I ask is it appears, i think, I should be able to delete this. The idle pick up and warm up relay seem to deal with the anemic 22re original found in the 4 4runner. I won't have those power issues.
 
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What exactly does the amplifier do? The reason I ask is it appears, i think, I should be able to delete this. The idle pick up and warm up relay seem to deal with the anemic 22re original found in the 4 4runner. I won't have those power issues.

The AC amplifier is crucial as it is the control for when the compressor starts and stops using the thermistor in the evap box, otherwise your evaporator will form ice, freeze up, and possibly crack. It also performs idle up duties. My 4runner doesn't have the warm up relay shown in the prior diagram.

acampdesc.JPG
ac-amp-front.jpg
 
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Is it the thermo resistor that cuts the power to the AC before freezes or is it the thermo resistor? I think one cuts the compressor if you were to be low on charge so it doesnt get so hot you burn the compressor and the other prevents freezing.


I won't have a 22re ecu to feed the signal to the amplifier not a cool being that I have a diesel. I'm trying to figure out how to fool the amplifier and bench test this. Forgive me for dumb questions as my only experience with AC install at this point has been in a boat. My thermo resistor on the boat kills the compressor before freezing and the sensor in the expansion valve kills the compressor if it gets too hot(like sucking mud into the water intake)

My diesel ecu will have an output so the AC clutch isn't engaged during start up. The idle control is also built into the ecu programming as it will maintain idle rpms with the extra load.

Screenshots_2021-02-14-11-39-10.png
 
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Is it the thermo resistor that cuts the power to the AC before freezes or is it the thermo resistor? I think one cuts the compressor if you were to be low on charge so it doesnt get so hot you burn the compressor and the other prevents freezing.


I won't have a 22re ecu to feed the signal to the amplifier not a cool being that I have a diesel. I'm trying to figure out how to fool the amplifier and bench test this. Forgive me for dumb questions as my only experience with AC install at this point has been in a boat. My thermo resistor on the boat kills the compressor before freezing and the sensor in the expansion valve kills the compressor if it gets too hot(like sucking mud into the water intake)

My diesel ecu will have an output so the AC clutch isn't engaged during start up. The idle control is also built into the ecu programming as it will maintain idle rpms with the extra load.
The Toyota system just uses a thermistor in the evap box which is basically just a thermometer(temp sensor) for the AC amp to control freeze/thaw cycle by cycling the compressor on/off . The AC amp is the control for the AC system and can't be removed unless another similar control was used.
The input from the 22RE ECU you referred to is actually just the tach signal input coming from the ignitor. I have not tested whether the AC amp will still function without this input (it might). I have not played around with diesel swaps so I don't know what type of tach signal is used or how to modify it to work with the AC amp.
I understand that you don't need the idle up feature so you can ignore that part of the wiring.
I think it's doable to integrate the AC amp into your system.
 
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Thank you! So long as know how the thermo and pressure switch work I can bypass or fool the amplifier. If both switches are n/c they will be easy to wire into a 5 prong relay, run them inline to the switch power feed for the relay. I will still have the safety cut off features to not blow out all the o rings in the AC system as well as avoiding burning up a compressor if it freezes. Im trying to keep the wiring simple. 2 relays for the AC system, one for the secondary electric fan that excites when AC is on and one for the compressor. I'm using a painless 70s gm pickup wiring harness assembly to rewire the entire rig. I love yotas, Hondas and my VW diesels but they make things like electrical systems overly complicated at times! If you can diagnose a 1996 Murray riding lawnmower electrical issue you can diagnose a 70s GMC electrical issue.
 

yotadude520

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Great write up man! The only thing I will mention is that you want your TXV bulb directly against your suction line
(no insulators) the TXV (expansion valve) needs to read the true temp of that suction line in order to accurately meter refrigerant into the evaporator coil. The heat shrink will slightly skewer the effectiveness and efficiency of your system. I wouldn’t worry about it now but for anyone in the future. I think if you wrap it tight enough you shouldn’t have a concern about a rub through.

Solid advice - that would make sense. I'll update the post!
 

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