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compressor wont shut off

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  • compressor wont shut off

    Hello all

    kobalt 80 gallon air compressor

    The compressor does not shut off when i turn the pressure switch to the off position, or when it reaches the cutout pressure.
    When i put the pressure switch in the off position the bleeder valve beside the pressure switch leaks air. It also does this when it reaches the cutout pressure.

    Any advice would be appreciated

  • #2
    Re: compressor wont shut off

    I'm just guessing here and it's a pretty obvious answer but maybe you need a new pressure switch. Hopefully someone will come along that can shed some light on an easy way to check that out.
    Diapers and Politicians need to be changed often... Usually for the same reason.


    • #3
      Re: compressor wont shut off


      That's your first problem. Shoudda bought a RIDGID.
      (sorry, couldb't resist)

      It this unit is less than a couple days old I would just take it back no matter how much of a PITA that might seem to be. You might have a Monday build and it could be nothing but trouble down the road plus if you do disturb anything they could refuse to exchange it or give you a refund, so think hard before you do your own troubleshooting.

      Sounds like a defective pressure switch.

      Probably using a NC contact (low pressure closes the contact),
      and opens when the set pressure is reached.

      1. Pump up the tank until the relief valves pops off.
      2. Unplug the compressor.
      3. Using a meter (DMM, DVM, or analog meter such as a Simpson 260 [which is Woussko's favorite]) set to measure Ohms, place the meter leads across the C (Common) and NC (Normally Closed) contacts. The switch contacts should be OPEN with the tank pressed up so you should see infinite resistance (OPEN switch contacts which would shut off the motor).
      4. While monitoring the switch contacts with your meter, OPEN the drain valve on the tank to slowly bleed off the pressure until the switch trips. This will probably be about 10 to 15 PSI below the setpoint, but the deadband could be more or less by a few pounds.
      5. When the switch resets (contacts return to shelf state), you should be able to hear the mechanical movement of the switch if there is no noise. Note the pressure.

      a. If it doesn't trip by the time the pressure drops 20 PSI, it's probably bad.
      b. It could also be caused by a blockage in the nipple between the switch and tank. That's a problem with using the NC contact. If there is a blockage or the switch were to be physically separated from the tank then the pressure in the switch would go to zero which would close the switch and energize the motor. It's not fail safe logic but it the simplest (cheapest) setup and it works.

      You should study the diagram in the manual and understand and verify the configuration before testing as above.

      If this is a 220V compressor then the setup will be different and the switch logic could be reversed.
      "It's a table saw, do you know where your fingers are?" Bob D. 2006



      • #4
        Re: compressor wont shut off

        There appears to be quite a number of posts about Kobalt compressor problems and not just one or two types of problems either.

        In this case, it definitely sounds like the pressure switch has failed, especially when you say you cannot turn it off manually. I'm not sure what you mean when you say "bleeder valve"... do you mean the safety valve has popped open to relieve the continueing pressure build-up? If so this is a dangerous situation and you should take it back to Lowes for their attention.

        If it is another valve, like the pressure release valve located on or near the pressure switch, than that has probably failed, gotten dirty, or whatever. In that case, it would appear that the compressor has not truly reached it's cut-out pressure setting, because the pressure release valve is venting at a faster rate than the compressor can overcome. (But in that case, you should still be able to turn off the compressor!)

        (The pressure release valve is only supposed to open when the line reaches the maximum set pressure and the pressure switch shuts off the motor and opens the release valve to blow off the cylinder and line pressure to the pressure switch. This acts as an "unloader" so there is no pressure remaining in the cylinder or feed line to the tank... thus allowing the compressor to start again without load. If the pressure release valve didn't function at all, there would still be pressure in the cylinder and the motor would most likely overload and stall because such pressure would be holding the piston from moving.)

        I hope this helps,