1UZ swap and Air Condition

The 1UZFE EGR Delete Kit is available for sale here.

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fresno,ca
Thanks to this website and many other write ups, I was able to finish my swap! And NOW need 1 more thing. AIR CONDITIONING. I didn’t think it would be that complicated. But I have run into a dilemma. I have researched that I need to trick the ECU. But no where would give a hint how to trick the ECU. Maybe Im not understanding the AC wiring operations well enough…

Here is my problem:

I plumbed with custom hoses and used the 1uz compressor. My AC switch inside will not activate the compressor clutch. When I do override and add 12v, the clutch will engage. This has allowed me to add R134 and allow me to have cold AC when IDLE only… BUT when on idle, I am not able to drive it, as it seems like the tranny will not operate correctly. Which I have found it may be related to the AC. When idle-ing, it is very low, it is NOT idle-ing up.

When testing the wire to clutch I get 11.8v constant with or without the AC switch.

My research has led me to believe the 1uz has its own AC ECU, which gathers information about the pressure switch and so forth.. Once enough info is gather, it then sends a signal to the ECU, which in turns send the signal to the clutch and idle up valve.. My ECU only has 2 wiring related to the AC; AC & ACMG. AC goes from ECU to the AC ECU and ACMG goes from ECU to clutch.. Im assuming the AC wire sends info from AC ECU to ECU. THEN the ACMG would send the signal to turn compressor clutch ON/OFF.. I could be wrong, please help clarify. It’s a 92 Lexus SC400 USA engine.. Thanks in advance.
 
On some older toyotas, AC is active low input of engine control unit, and ACMG is output which activates relay which in turn activates the clutch.

Newer (from mid-90's on) toyota/lexus run more complicated system. a/c on/off signal is transmitted to engine control computer digitally,in addition to that a number of signals is fed directly to ECU like outside temp , pressure switch, clutch RPM detect signal.

If you're double sure that a/c related signals to your ecu are only AC and ACMG then AC signal is on/off one
 
you are correct... the AC wire is the input from the AC control unit which sends a + signal to the ECU. The Output wire is the ACMG, and it will trigger the AC compressor. i add 12v to the AC wire from the ECU and it did work. only problem is, it idles really low and and it seems like there is a heavy load on the engine with it having a hard time to rev. i did see a little freon spraying out from the relief valve... I checked the belts and it is not tight. I dont have any check engine lights.. now im really confuse...
 
I just hooked up the clutch wire and everything worked perfectly in my x8 cressida.

man your so lucky to have AC in you project. i wont even drive my without AC.. I wish it was that easy too... before I swap in the 1UZ, it was working perfectly.. I think it may have to do something with the wiring or some communication to the ECU.
 
engine controller has little to do with the a/c. Especially if you assume there's too high pressure in the system. Normally, a/c system must include 3-way pressure switch which signals abnormal pressure (too high/too low) and turns the compressor off
 
make sure you have radiator / condenser fans running or the gas pressure will go through the roof and stall the compressor, preferably have the high/low gas pressure switch connected! also make sure the ACMC wire from the ecu is not directly connected to the clutch and is connected by a diode back emf suppressed relay
 


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