[FrankJ]

The pressure switch is to some degree adjustable. And you are correct, by rule you cannot break the seal & adjust it. There was a lot of discussion as to what was allowed under 2014 rules. This year's rules is very specific. The legal pressure switch should shut off at about 115 psi, rising. It should turn back on at 105 or so. If yours does not do this, try a different pressure gauge. If it really shutting off at 90 PSI you should get another switch or send that one to Nason to be calibrated.

The switch drives a digital input, either to the PCM or the RoboRIO. If in the PCM, the PCM controls the compressor. If to the RoboRIO, you would have to program it, but still it should turn off & on by switch, not by speculation of the programer.