[blime81]

You said the switch is giving power to the relay but is the relay giving power to the compressors once it gets power from the switch? The relay should click once it gets power.

You can check if its the pressure switch by simply making a jumper and by passing it.

Are your compressors fused (they should be)? If they are they might be fused off one big fuse that blew.

Check one thing at a time.