evo_gerard Posted March 15, 2023 Report Share Posted March 15, 2023 good day everyone, I'm setting up an early model evo and i've encountered a weird issue. once the engine fires up the ac request cycles on an off with the clutch delay. Its connected to DI1 which has 12v whether the A/C is on or off. DI5 in the link installation manual is A/C switch (evo 3 only). this has 0v whether the A/C is on or off. Any possible solutions to this issue? troy-15-3-23.pclx PC Datalog - 2023-03-15 3;14;38 pm.llgx Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 15, 2023 Report Share Posted March 15, 2023 Looking at the wiring diagram I can see a possible scenario that could cause this. I suspect the 12V pull-up on Aux 2 could pass through the AC clutch relay coil and keep DI1 high. DI1 does have a pull-down on it to overcome this but some possibilities like an aftermarket relay with a lower resistance coil or missing diode could potentially trip it up. Can you try unplugging the AC Compressor relay, then check if DI1 state then changes correctly with the AC switch. If that works the easy fix will be to move the AC clutch wire over to a spare Ign or Inj output instead of an aux. An explanation of the circuit: The AC request signal comes from the "AC control unit" at top right, it will be 0V when off, 12V when on. It feeds through the triple press switch then down to pin 45/DI1. You will notice just below the triple press switch the AC request signal splits off to supply 12V to the AC clutch relay coil at the same time. The problem is, when AC is off, there will be a weak 12V coming out of Aux2 (pin 22) due to its pull-up resistor, this could be enough to pass through the relay coil and keep the AC request signal going to DI1 high. Quote Link to comment Share on other sites More sharing options...
evo_gerard Posted March 16, 2023 Author Report Share Posted March 16, 2023 Hi @Adamw got a chance to remove the relay. the cycling stopped. With the relay still out i tried turning on the A/C but it did not change the state of DI1. it just stayed off. I'll still reassign the A/C clutch and report back. Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 16, 2023 Report Share Posted March 16, 2023 Can you check if there is 12V on the Green/Yellow wire going into the pressure switch when you switch AC on/off (with AC Clutch relay unplugged), if it looks good there then check you the same coming out of the yellow/green wire that goes to pin 45. It sounds like possibly your gas press is low so the press switch is open. Quote Link to comment Share on other sites More sharing options...
evo_gerard Posted March 16, 2023 Author Report Share Posted March 16, 2023 10 minutes ago, Adamw said: Can you check if there is 12V on the Green/Yellow wire going into the pressure switch when you switch AC on/off (with AC Clutch relay unplugged), if it looks good there then check you the same coming out of the yellow/green wire that goes to pin 45. It sounds like possibly your gas press is low so the press switch is open. will check that. the car has been sitting for 2 years so i think the pressure is low. thanks very much @Adamw. i greatly appreciate your insight and advice Quote Link to comment Share on other sites More sharing options...
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