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"Mobile Air" compressor OF2513CW

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  • "Mobile Air" compressor OF2513CW

    Hello, having problems with a compressor, wondering if anyone has any ideas:

    Single stack air compressor "Mobile Air" unit, model OF25135CW.

    When I plug it in, it fills the tank (correctly). I can use that amount of air that is in the tank, but when it goes to refill the tank the motor hums and then shuts off. The compressor doesn't turn on, it just hums then shuts off. I have to open the valves, drain the tank and then plug it back in to get the tank to fill again.
    What could this problem be? Can I fix it myself?

    Thanks for any ideas, kind of lost on this one...

  • #2
    Re: "Mobile Air" compressor OF2513CW

    Check valve. Reference #32 on the IPL.
    Part #079027007030
    "HONK if you've never seen a gun fired from a moving Harley"


    • #3
      Re: "Mobile Air" compressor OF2513CW

      It could also be the unloader valve. Basically this valve releases the pressure in the cylinder when the compressor is not running. This is used on many lower end compressor since they cannot start against much of a load.

      Another possibility is that where you have the compressor plugging into has a low voltage condition, or you are using an extension cord that is not heavy enough and there is a voltage drop from that. Usually this will trip the circuit break.
      Last edited by whagen; 01-05-2010, 03:22 PM.


      • #4
        Re: "Mobile Air" compressor OF2513CW

        Most likely it is, as Whagen referred, the Pressure Release Valve (also known as an "unloader valve") that is mounted on the pressure switch where the line comes from the compressor cylinder.

        Actually all compressors (regardless of size or price) need some method to "unload" the pressure from the cylinder before they can start. While some use a "Pressure Release" type valve, the big monsters employ some type of "Free Air Unloader" design, either as a seperate mechanism or as in the case with industrial size units, directly on the valves.

        The Pressure Release valve appears to be an often cause of starting failure. Apparently they get dirty, but component failures are not rare either.

        When the compressor is running, listen to the shut-down, which occurs when the pressure switch senses the maximum pressure has been reached. The very moment the motor stops, you can hear a quick burst of released air... that's the pressure release valve venting the cylinder and the air that goes from the main line to the pressure switch. If you don't hear that little burst of air, then the valve is NOT working. In which case there's high (whatever the maximum PSI of the compressor is) pressure in the cylinder and feed line to the pressure switch and the motor will not be able to push the piston against this pressure.

        As suspected by Doctordeere, the "Check Valve" is located at the point where the air feed line taps into the primary tank. Basically, it's just a one-way valve that lets the air flow into the tank, but prevents it from coming back out into the feed line. Generally, failure with this valve is more rare; but, leakage can occur and you have the same symptoms, as the air pressure bleeds back through the line and repressurizes the cylinder.

        So either valve can cause the problem. But I'd check for the sound of "air release" first. If you think that's not the problem, the way to test the check valve is to slowly loosen the pipe or hose nut on the feed line (slowly, as this line is under pressure). You'll hear the air being released from the line... but, it should only be for an instant! If the air release is longer, you should see the pressure dropping in the tank, which then indicates that the check valve has failed. If the air does NOT drop in the tank, then it's the problem is with the release valve. Either valve may only be dirty though, with some grit or debris keeping the spring or actuator from seating the valve properly.

        I hope this helps,



        • #5
          Re: "Mobile Air" compressor OF2513CW

          I had the same problem,but you need to make sure you plug it into a 20 amp outlet [it needs a full 20 amps to run]or it will keep shutting down. OK?


          • #6
            Re: "Mobile Air" compressor OF2513CW

            Originally posted by MMarsh417 View Post
            I had the same problem,but you need to make sure you plug it into a 20 amp outlet [it needs a full 20 amps to run]or it will keep shutting down. OK?

            Not many homes equipped with 20 amp plugs. You can identify a properly installed 20a plug looking for the sideways hot on the left side and a 20a breaker in the panel. If your appliance has this sort of plug, it is 20a, otherwise it should work just fine on a 15 as it is going to be 15a or less. Depending on when the home was made, exterior plugs should be 20a, but that is not a promise, folks have done weird things. The compressor in question pulls a whopping 9.6 amps, it should run damn near on lamp cord. I have owned compressors that are testy and will not run on extension cords, but those pulled 13 or so amps and that model had a habbit of being testy once it got past the warranty *cough* DEWALT *cough*

            I find that difficult compressors require longer hoses, and need to be plugged directly into the plug and not into an extension cord. If you do have to use a cord, it needs to be a 12 gauge one, the thick heavy duty ones.
            We don't have preventative maintenance around here, we have CRISIS MANAGEMENT!


            • #7
              Re: "Mobile Air" compressor OF2513CW

              It does NOT need 20 Amps or it would not come with a standard 15 Amp 110v plug.

              This unit pulls 9.6 Amps according to the sticker (as MasterBeavis said), I have one, so, a regular household outlet will do just fine - as long as there isn't anything else with heavy power draw running simultaneously. I typically have a small table saw, chop saw, compressor, router, etc plugged into one side of the garage or on an extension cord and just use one at a time. Away from the house, I use either a 100ft 14 gauge or 25ft 12 gauge extension cord and haven't had issues with either. So it is not power draw in this case. Other units have other requirements.

              It is an issue with the valve.