Electrical 89 fox AC help please

The AC compressor circuit on these cars is relatively simple.

You didn't say what they jumped out to get it to work so we can't assume anything. What i'd do is turn the AC on and test for power at wire 348 at the low pressure cutoff switch. You should have 12V on the light green wire. If you do, try installing a jumper wire here and see if the AC turns on.

The WOT relay is a common problem area. The wire insulation cracks and falls apart and the plug needs to be replaced. The relay should be normally closed and only opens at WOT, so you should have continuity across the terminals for wire 883 and 347

This wiring diagram is for 1993 but should be the same wire colors and numbers for 1989. This one is just a lot easier to look at vs the '89 diagram.

What’s the ambient temp and what’s the high side pressure?

If it’s cooler out, the system will cycle. The ambient temps keep the system pressures down so you will hit the 20 psi limit a lot sooner.

Generally the high side pressure should be 2.25-2.5x the ambient temp.

hold 1500rpm, turn ac to max with doors open, let stabilize for 30 seconds and then record high and low side pressures and make not of outside temp. That will allow us to make a better assessment of system performance.