Porter Cable pancake runs over 150 and blows prv

by Ian Fratar
(Oakland, Ca)


It started with the regulator hissing and the compressor trying to build as it leaked from the area around the regulator. I carefully inspected the plastic diaphram and put back.
Now, it doesn't seem to leak as bad - YET, now it actually runs to fill the tank till over 155 PSI and then the pressure relief valve blows open, of course.
Where is the whatever component that makes the motor shut off before 155?

I greatly appreciate that this site exists and hope that help on my issue exists.


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Dec 08, 2015
pressure switch / PRV
by: Doug in s.d.ca

Hmmm. One thing at a time.

Let's try a diagnostic:

Unplug the machine and then disconnect one of the wires that goes to the pressure switch. Tape or cover the wire so that is doesn't touch anything, and then plug in again.

Does it run?

whether it runs or not, unplug and reconnect the first wire and disconnect the other wire in the same way, and plug in again.

Does it run now?

It should not run either way. If it does, there is a short in the wiring other than the switch.

If it does NOT run, then the wiring is correct, and the pressure switch is bad, or wrongly rated.

Dec 07, 2015
Frustrated C2002 owner
by: Bill

Ian, according to the specs the PORTER-CABLE C2002 0.8 HP 6-gal 150 PSI Pancake-Tank Electric Air Compressor by Porter Cable is supposed to shut off at 150 PSI.

If your PRV is letting go at 155 PSI, and feeling that the gauge accuracy on these cheaper compressors is always suspect, I surmise that your air compressor is not reaching the pressure necessary for the pressure switch to stop the power supply to the motor, and that it's the PRV that is the problem.

I would be inclined to push in on the end of the PRV when it starts to release air, and let the compressor run up to 160 PSI and see if it shuts off by itself. Typically PRV's let go after reaching pressures higher than 5 PSI over the set point. I'd be comfortable watching the pressure get to 160 before letting the PRV release.

If the pressure gets to 160 PSI and the compressor doesn't shut off, then it's got to be a bum pressure switch as far as I'm concerned.

Dec 06, 2015
by: IanF

Thanks for your response!
Yet, I'm still stumped, because the cut-in and cut-out settings on my pressure switch are .... not simply listed..... yet they were exactly designed as replacements for the C2002 150psi type 7 Porter Cable pancake compressor?

And if I were install in improperly, .... how?
As it's a tube and switch with only two holes to attach, would it either work, pinch, leak, or be hook-ed up backward? I don't know what other option of incorrect install would be.

Maybe it's time to get a different brand of compressor than Porter Cable?

Sorry, I'm frustrated.


Nov 28, 2015
New pressure switch
by: Bill

What are the settings - the cut out and cut in pressures settings - on your new switch?

If the compressor tank pressure bypasses the cut out pressure setting and the PRV lets go, then either the switch is faulty or it's been installed improperly.

First thing though, do you know what the settings are supposed to be?

Nov 28, 2015
follow-up still a problem
by: Ian Fratar


This is a real query, as I've written before, and swapped out several parts:

On my 6 gal C2002 (type.7), I have carefully checked the plastic diaphram for leaks, changed the safety valve (4) "pressure relief valve", and changed the pressure Switch (111) -------
YET, the NEW safety valve blows at 145-155. The NEW pressure switch does not seem to cut the engine off.

Any idea what is going on?

I'm real glad this site exists.

Aug 20, 2015
pressure switch / PRV
by: Doug in s.d.ca

This is a C2002?

The pressure switch is under the cover, near the power switch on a bracket with a hose to the manifold (or possibly the tank, can't tell for sure). If that came off or is leaking, you'll have this symptom. Item 111 on the parts list.

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