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.