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R32 Skyline AC engagement.


Kanaric
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Having an issue with the AC in my 89 Skyline GTS-T. A shitty tuner tuned the car in Arizona and I got the car back and brought it to a guy who knows what he's doing to fix it. I'm sure the Arizona guys messed something up. 

Basically the ac compressor clutch will not engage. Originally I thought it needed to be replaced because it was on it's last legs, so I did. However the new compressor didn't work as well. I loaded up the Link G4 software and when I turn on the AC nothing changes, it doesn't see it as being turned on. However if I change "On Level" from high to low (or the reverse, forget which) for AC clutch it does turn on and I can hear it turn on and it starts to blow cool air. 

I have it at an AC specialist right now and he's claiming that the wiring is good and they have used an AC control unit from a R32 GTR that is known to work and it still won't turn on. 

I'm not in front of the software right now but i think the two values are aircon clutch and aircon request. I've tried changing the settings in both and neither fixed the issue aside the clutch engagement. The runtime shows them as always off unless I mess with the "on level" setting. AC request never shows as on. 

I'm guessing the AC guy is just wrong and there is some kind of electrical issue but I want to make sure there isn't anything i'm missing here since I had who I now know to be a terrible tuner initially set this up. I have a Link G4+ GTRLINK. I'd put the serial number in my account but right now like I said it's at the AC shop. 

Thanks for any help or suggestions. 

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It sound like your problem is that the AC/heater control module signal isnt being received/understood by the ECU. (this is the AC request, and should be wired to one of the digital inputs). Its also possible you have some incorrect settings in the ECU so that an incoming request isnt triggering clutch output. Your first check should be fire up the runtime values screen (f12) with the laptop connected, and see if you see the AC request DI register as "ON" when you press the AC button on the control unit.

If you can make the clutch engage by swapping the polarity of your AC clutch output from low>high then the wiring from the ECU to the physical AC clutch on the engine is ok. You should set the polarity to whatever makes it OFF under normal circumstances (polarity low = on if your wiring is the same as the diagram i'm looking at).

You will either need to check your wiring diagram or with a multimeter, but the one I'm looking at says the AC amp grounds pin 15 (connects to pin 46 on the factory ECU) to make an AC request, and that the test to check you AC functionality is to ground this pin at the ECU and see if AC starts working. This means you should have the relevant DI set up as AC request, on level = low, and probably pullup=on. This should be enough to get the AC request to be triggered in the F12 screen and then we can look at how the ECU is controlling the AC clutch.

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The AC Request comes into the ECU on pin 46 (see position below).  From what I can see I think it works opposite to how CJ interprets, this pin should be close to 0V when AC is off and about 12V when AC switch is on (anything more than 1.5V will be acceptable).  Which way around it works is not so important anyhow, the main thing we want to ensure is that the voltage at this pin 46 changes when you switch the AC switch on/off.  Check that and report back.

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Quote

Your first check should be fire up the runtime values screen (f12) with the laptop connected, and see if you see the AC request DI register as "ON" when you press the AC button on the control unit.

It doesn't. I tried this after reading a related post here. 

I'll try these suggestions, thanks guys. 

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