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mk3 mr2 AC Clutch Control Setup


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Your config looks like its running a 2GRFE right? What car is this engine out of? Probably a good idea to get the service manual for the donor car and see how the factory aircon control is supposed to work. If you're lucky the majority of the system will be independent of the engine and ECU and the only signals you'll have to deal with are aircon clutch trigger (usually low polarity to enable it) and a "aircon is on" signal. 

Depending on the donor car AC system there may be a bunch of signals around water temp, AC line pressure, AC request switch on the dash. If you're lucky all of this will go to the AC amp and you can leave it do do its thing and just deal with 2x signals I mentioned above.

Are you keeping the mr2 aircon amp or trying to run all the safety stuff (pressure switches etc) from the ecu directly?

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Check the factory wiring diagram for what connects to the AC amp directly. I dont know about ZZ30's but in the SW20's a lot of those signals about rpm, coolant temp, ac pressure etc all were directly wired to the AC amp and so it was all independent of the ECU. In fact depending on the model you only got 2x wires into the ecu that effected the AC, one was a "ac is on" input signal from when the AC clutch was engaged, and the other was a wire between the AC amp and the ecu that the ecu could ground out to make the AC switch off. To set up your own rules for that you would follow Simon's instructions above once it's wired in.

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