Compressor not stopping at 120psi

[Gary Dillard]

First - check across the terminals of the pressure switch with an ohmeter while you are pressurizing the system. I think it is a normally closed switch so you should read some resistance value until you reach about 120, then it should go to off-scale because the switch has opened. If you don't see that happen, you have a bad pressure switch.

Next, check on the driver station what you are seeing from the digital I/O port where you have the pressure switch as you go up in pressure. It should read true as you go up then change to false at 120 (or vice versa). If you don't see this then you have a bad connection somewhere between the switch and the cRIO - check the wiring.

If those are both good, your problem is in software. There is a pressure switch vi that should be running all the time - make sure you have it in place.