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AC problem FD rx7, LINK G4+ plug in


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Hey guys, I have a stock twin turbo series 6 FD rx7. Just recently upgraded to link G4+ plug in. I have noticed that my AC no longer works as previously using stock ECU.

The AC compressor would only engage at certain fan speed (1,2,4) with the AC button depressed, and majority of that time I was unable to disengage the AC compressor after its been turned on, even though I have turned the fan speed to OFF.

I was told that my AC switch dial may be failing, however when I plug my factory ECU back in, everything works normal.

I have tried cleaning the dial with electrode cleaner, but with minimal luck.

Lastly, the compressor no longer run at certain interval like factory rx7 when turned on. It will stay running all the time with no pause. Even with blower fan turned off.


I would love to enjoy driving around with a functioning AC in the hot summer days, please help me guys.


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The Air con switch requests the air con be engaged via DI3 - First thing to do is try it with the pull up on as in the attached picture.

If you Press F12 and look at the status of DI3 does in change to green? if so does it change to green when AC Request is on ? if not then change the on level to high.


The Air Con Clutch control settings under Chassis and body may also be set wrong, if the inj duty cycle is above 35 then it will switch off, so if you have your master fuel set low and your above this amount of inj duty cycle it will also not work.


Screenshot 2019-01-13 at 12.34.15.png

Screenshot 2019-01-13 at 12.39.16.png

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Thank you for replying ClintBHP

The problem I am having at the moment is unable to switch the AC compressor off once it is on for awhile, as well as unable to have the compressor run like stock ECU (AC clutch engages and disengages at an interval automatically without me touching the dial). I am worried that this might over pressurise the system and damage something.

I have AC request come online when I press AC button, at the same time AC clutch also come on board.(F12 status)

If I only just turned on the AC, I can still turn it off by unpress the AC button or by turning the blower fan dial to OFF(AC request and AC clutch would go offline as should)

However, if I leave the AC running for awhile (more than 1min) I was no longer able to turn the compressor off using the AC button or blower fan dial. (F12 status indicate AC requrest and AC clutch remain online constantly).


The settings for AC clutch control was set based on TP position, and clutch off value was set to 40.

Only other setting that was different from basemap was the AC clutch polarity. I have mine set to "LOW" instead of "high" provided in the basemap.

Because only low polarity allowed me to turn on AC with the AC button depressed. If I have "High" polarity, the AC clutch will engage even when the blower fan switched off.


Also in the F12 Aux function page, the AC pressure and AC evaporator temp never changed, always at a constantly 37.7psi and 10degreesC respectively. Is this normal?

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The pull up resistor when turned on prevent everything from turning on, the AC request would not even come online with AC depressed.


And if I change the on level from low to high then AC request would be on all the time and unable to turn off even with blower fan switched off.

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The AC control all hinges on what the Di signal into the ECU is doing. 

When the request is active we will activate the AC clutch. When the request is removed we then disengage the clutch.

On the RX7 the request signal tended to sit a bit high so we have a 10K pull down resistor and a diode in series to lower the voltage that the micro sees.

Ideally you need to measure the voltage at the AC pin (79) and see what that is doing on the factory ECU and then compare to on ours.  

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