Won't stay at pressure

by jim M
(Riverside Ca)

porter cable pancake c2002, i just changed the pressure switch but didnt help. when i first plug in the compressor it will reach 150 psi. but after running some air out it wont reach 150 again it runs and stops and runs and stops, wont keep pressure up. any ideas.

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Bill says...

Hi Jim. If I understand correctly, the pressure builds normally to 150 PSI, and then when you use air, the compressor starts and stops.

At what pressure level does the compressor re-start? Is it at the normal cut in pressure, or at a higher level?

Once a compressor starts running, unless there is an electro-mechanical issue, the only thing that will stop the compressor is the pressure level reaching the normal cut out pressure, and the pressure switch reacting to that pressure by shutting off the power to the motor.

By the same token, the only thing that should allow a compressor to start is that the pressure in the tank is at, or below, the normal cut in pressure level. The pressure switch reacts to the lowering pressure level when that level is the cut in point, the pressure switch closes, and electricity flow to the start capacitor and motor to fire up the compressor again.

Everything that you've said indicates to me that your pressure switch is improperly wired, or the settings are incorrect, or the switch has failed.

Cheers,

Bill