[Tom Line]

Can you please explain what you mean by it 'works'?

Does it pressurize and shut off at the correct pressure (around 125), or does it simply keep running? Does it start again when the pressure drops below 80?

The pressure switch should be feeding back to your digital I/O on your digital side car, and the spike that powers the compressor should be fed from one of the relay connectors on the sidecar.

You absolutely need to power your digital sidecar.