AC not working - need help

[Pixel6]

Hi guys.

I’ve been troubleshooting my AC issue, and think I’m close but need help.

This is on a s13 Silvia.

When I press the AC switch, the clutch doesn’t engage. When I jump the pins On the engine bay relay, the clutch engages and blows cold air.

I believe the issue is with the control pin #43 that goes from the eccs head unit to the relay.

So my question... does that wire lead directly from the eccs head unit directly to the relay? Or does it go to the ECU first. The reason I ask is that it worked until I had the ECU replaced with a ProEFI ECU.

The issue seems to be a control disconnect between the head unit, and the relay.

[jedi03]

what is your pressure when you jump the switch? if the pressure is ok could be the pressure switch...are all your fuses ok, is your wiring between the two points ok?

[ultimateirving]

Hey man, I have a/c in my s13 with SR. Check the pressure switches as noted. If there is low/no refrigerant, the clutch will not engage. Also, I have replaced the Climate control box as it had gone bad and wouldn't switch on the A/C Clutch.

I am not sure if the factory wiring runs through the ECU; I am using a ROM-tuned ecu.