My compressor won’t shut off

I’ve received a number of questions on my ASK page wondering what’s wrong with a compressor that it won’t shut off. Further to that, one writer indicates that the PRV (pressure relief valve) pops every time he uses his compressor.

If your compressor won’t shut off, you are flirting with a very dangerous situation. The compressor will keep compressing air into the tank until:

a)it can’t compress any more because there’s more pressure in the tank than the compressor head can overcome

b)the pressure relief valve opens to safely vent tank overpressure

c)neither of the two above happen, and your compressor tanks undergoes catastrophic failure, with significant risk to all and sundry around

We hope that the PRV works.

Regardless, if the compressor won’t shut off, you need a new pressure switch RIGHT NOW. Don’t delay. Your compressor is in trouble, and so could you be if you don’t replace the switch. Here’s one source. But regardless of where you get one, get your pressure switch replaced.

5 Responses to My compressor won’t shut off

  1. Bryan says:

    when my compressor kicks on the pressure in the tank is about 70psi it is supposed to stop at 90psi or so. but it doesn’t stop or ever seem to get to 90psi. it sound like there is an air leak. Could that be the pressure switch?
    Hi Bryan:

    Please go to, click on the ASK button in the nav bar, and enter your question there. Add as much detail about the symptoms as possible, if you would.


  2. Will says:

    How right you are for this article you wrote! I was just shopping for a replacement pressure switch when I came across this page. Just the other day (and I consider myself lucky!) I was using my DEWALT D55146 compressor to clean some parts totally not paying attention to why the compressor has not shut off yet when enough pressure built blowing the pressure gauge off the manifold.

    I was lucky the pressure gauge was the only thing that went and that I was not in the way when it blew it’s top (I know it just a small gauge but I bet it hurts like all get out if it hits skin!)

    I consider myself fortunate that all this cost me was a 22 dollar gauge and a 63 dollar pressure switch and a little down time until the parts show up from Dewalt:-)

    Good advice you gave.


    Thanks, I appreciate the feedback.


  3. Mark says:

    My Dewalt D55140-1 compressor did the same, I looked up the pressure switch for mine, but I think it was $19.00 ish any way I pulled mine out to find rusty water in the line and it plugged the pressure switch. I cleaned the line, cleaned out the switch and it is fine. Pressure switches do fail but not often.
    Try to save you a buck. My compressor pumps to 130 psi, put it blows off at 140 psi.
    Good Luck!

  4. Paul Stockton says:

    hey how do i crank mine past one fifty to about two fifty

    • Bill says:

      Paul, if the question is how to “turn up” the output pressure from your compressor, from it’s rated 150 PSI to 250 PSI, the basic answer is, you can’t. Sure, you can monkey with the pressure switch settings to adjust the cut out pressure higher. Yet, your air compressor comes preset to the cut in and cut out pressures for good reasons. One of those is the motor strength and the sheave size and the engineering that went into the design optimized that design for the cut out pressure it is rated for. Second, if you try to over pressurize an air system, you may have failure. Essentially, if you need a 250 PSI output air compressor, that’s what you buy. Good luck.

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