[ebarker]

two debug steps, do both,

step 1) disconnect the wire from the pressure switch

step 2 - verify control system) start the machine, enable the robot/cRio, and take the two stripped bare wires that were connected to the pressure switch and touch them together. the compressor should cycle on/off as you close/open the two wires. if it doesn't then you have a control system problem.

step 3 - verify pressure switch) connect an electrical meter in resistance/continuity mode to the pressure switch. start the compressor and watch the pressure gauges and meter. as the pressure passes 115psi the continuity should change on the meter. this will verify the pressure switch. make sure to wear safety equipment, monitor the pressure, and think. the relief valve should relieve at 120 psi. if you go past 125 psi vent the system down, turn it all off, and inspect the relief for safety.

basically you need to decouple the switch and control system and test independently.