Reasons Why An Air Compressor
          Will Not Start



Knowing how aggravating that is, here are some reasons the compressor will not start, in the hope understanding them will help you get your air compressor back on track.

Here are a few of the things you need to look at when your air compressor just will not start.

The Basics of Compressor Starting


Silly question I know, but is the compressor electrical power plug in the wall socket? Check to make sure that it has not fallen out of the socket as your first check.

Plug in? OK, then your next check is....

Can you get to the electrical service / power panel in your garage or house? Have a look inside it and see if any of the breakers are tripped, or fuses are blown. If so, reset the breaker or change the fuse.

Or, plug a trouble lamp into the same socket that the air compressor will be plugged into, to make sure that there is actually power getting to the socket.

Fuse or Breaker Blows Again


If the compressor is creating the electrical fault, then the breaker will pop or the fuse will blow once the compressor tries to start again.

If the compressor still will not start, look along the wiring path for your compressor and make sure, if it has an in-line fuse, that it hasn't blown, or if there is a reset button, give it a push.

Having done these quick checks, you will now have identified for sure that the air compressor is the source of the electrical problem.

If the breaker or fuse lets go when the compressor tries to start again, you have an electrical problem at the compressor. That might be pressure switch shorting out, a start capacitor has failed, the motor is failing or overloaded... there are a host of reasons, covered on the Troubleshooting pages on this site. More on this includes...

Is There Pressure In The Tank?


Next check...look at the gauge on the compressor tank. Is it showing pressure? Is that pressure reading higher than the high pressure cut-out of that compressor?

With the air tank empty, the danged compressor still will not start?

the Pressure Switch?


Unplug the compressor. Drain the tank down to zero. Close the drain.

Pull the cover from and get down close to look into the pressure switch and have someone else plug the compressor back in or turn it on. Do you hear anything happen? Do you see any movement in the pressure switch?

You might hear a click as the pressure switch trips due to low pressure and the points in the pressure switch should move, to allow them to connect, and send power to the electric motor.

I Heard A Click From The Pressure Switch


If you hear a click from the pressure switch when the compressor is powered up and you saw the points move, then the pressure switch seems to be working, and it is now sending power to the motor.

Can you check that? If you have a multimeter, you can check to be sure that power is actually flowing across the pressure switch to the motor circuit. And, if you have that multimeter, you don't have to kneel down and listen, just dump the air from the tank, power up the compressor, and check if power is getting to and flowing through the switch.

If the motor does not start at this point, and it is getting power, what is the motor trying to do?

Humming Compressor Motor?


Are you hearing a humming sound, or is any noise coming from the compressor motor? If not, double check for a thermal overload button or a reset button on or around the motor. With the compressor plugged in, push that button. What happens?

If the compressor motor starts, this suggests that it went out on thermal overload, and you may have an overload or motor overheating problem.

To check, when the tank pressure gets up to the cut out level, and the compressor stops, bleed the pressure down again. If the compressor restarts, well, just carry on. the motor has cooled sufficiently to allow it to restart.

If the compressor motor balks at starting again, it may be the start capacitor or the motor itself that is causing the problem. Or...

Make Sure The Unloader Valve Is
           Actually Unloading


Monitor the unloader valve when the compressor cuts out (if the compressor starts once it cools) to make sure the unloader valve is working.

If the unloader valve does not operate as it should that may be why your compressor will not start the next time the pressure switch sends power to the compressor motor.

Hope these tips are helpful. And, of course, if you still need help, just ask.