Reasons Why An Air Compressor
       Will Not Start

Some reasons the compressor will not start and man, is that aggravating.

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

The Basics

Silly question I know. But is the compressor electrical 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, 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 power at the socket.

Fuse / 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. This does not just apply to the fuse or breaker in the main panel, look along the wiring path for your compressor and make sure, if it has an in-line fuse, that it hasn't blown.

You will now have identified for sure that the air compressor is the source of the electrical problem, and if the breaker or fuse lets go when the compressor tries to start, you have an electrical problem at the compressor that might be caused by a bum pressure switch, a start capacitor has failed, the motor is failing or overloaded... there are a host of reasons, covered on the Troubleshooting pages.

Is There Pressure?

OK, the fuse / breaker for the wall socket into which you have plugged the compressor cord is fine. What is next?

Is There Pressure?

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? If you are not sure, leave the unit plugged in and either bleed air from the tank through the air tool or (I suggest you wear a work glove) reach under the tank and open the tank drain valve and let the tank completely empty.

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

Pressure Switch?

Unplug the compressor. Drain the tank down to zero. Close the drain. Get down close to the pressure switch and have someone else plug the compressor back in while you are closely monitoring the pressure switch. Do you hear anything happen? Do you see any movement in the pressure switch.

If not, and assuming you have got electrical power flowing to the pressure switch, by plugging it in with the tank at zero pressure, you should hear a click as the pressure switch trips due to low pressure. It should trip and send power to the electric motor.

I Heard A Click!

If you hear a click from the pressure switch when the compressor is plugged in / turned on, then the pressure switch seems to be working, and it is now sending power to the motor.

Can you check? If you have a multimeter, you can check to be sure that power is actually flowing to the motor. And, if you have a multimeter, you don't have to kneel down and listen, just dump the air, plug in or start the compressor, and see if power is 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?


Are you hearing humming, or any noise coming from the motor? If not, look 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, and monitor the start sequence. If it restarts, well, just carry on. If the 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

Also, monitor the unloader valve when the compressor cuts out to make sure it is working. If the unloader valve does not operate, that is a good reason 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.