It isn’t any fun when we go to use an air tool and an air compressor will not start to allow the air tool to be used. Very darned aggravating, indeed.
There are many types of air compressors in use around North America, and though many of them look different than other air compressors, and they certainly vary in size and other area, there are similarities that will allow you to check and see why “an air compressor will not start , by yourself and hopefully not taking it to a shop which is both expensive and time consuming.
To try an help you diagnose why your air compressor will not start, here are the steps I would use on my own air compressor.
Is there power to your air compressor?
I know, I know, it’s a dumb question, but needs to be asked.
If you are using a power bar or power strip… don’t! Plug your air compressor directly into a wall socket. The power strip may have failed.
If you are using and extension cord… don’t! You are putting a choke on the power to your compressor unless the extension cord is 25′ or less, and at least 10 gauge.
Move the air compressor to get it close to the wall socket, make sure there is power at the wall socket, and plug your compressor in there.
Air compressor will not start … read on!
Is the compressor switch on?
If your air compressor is one of those that comes with an ON/OFF switch, either separate from or part of the pressure switch, do please make sure that it is switched to on.
Of course, if you have been using the compressor and it won’t start, the power switch will likely be on already. But just in case, please check it anyway.
What is the air pressure in your compressor tank?
When my air compressor will not start I always check the tank gauge to see what the pressure reading is in the tank.
The reason for that is if the pressure switch is set with a cut in pressure (the setting at which the air compressor will start) that is below the air pressure currently in the the compressor tank, then your compressor pressure switch has not tripped to on, no power is flowing to the air compressor motor, so the motor cannot start.
Even if the air pressure in the tank is below the air compressor cut in pressure setting, part of the diagnosis as to why it won’t start, is to empty all of the air out of the compressor tank.
Try emptying the compressor tank
Unplug or shut off the compressor.
Drain the air tank by attaching an air tool or blow gun to the hose and blowing off all the air, you can drain the compressor tank by opening the tank drank valve and allow all air (and any trapped water) to blow out the tank drain which you should do regularly anyway, or you can empty the compressor tank and test your air compressor pressure relief valve at the same time, by pulling on the PRV ring (wearing gloves is a good idea). This will allow all the air to blow out of the tank as well as making sure that the PRV internal workings actually do work. After all the tank air is gone, push the PRV valve back in and your PR Valve is reset.
Why empty the compressor tank?
By draining the tank you are emulating the function of the unloader valve just in case the one on your air compressor is not working properly. A complete description of what the unloader valve is and does is on the unloader valve page.
Emptying all of the air from the air tank allows any air trapped over the compressor piston – or compressor pistons – to escape out through the tank as well. If there was trapped air, the additional load on the air compressor motor may have prevented the compressor from starting.
OK. Plug your compressor back in or turn it on… any luck with it starting? No? OK then, let’s carry on.
My air compressor will not start – still!
We know we have power from the wall socket to the compressor, we now know that a malfunctioning unloader valve isn’t the problem, we are going to assume that if your air compressor has an ON/OFF switch that it is turned to on, so now what?
Is power getting to the compressor motor?
Knowing that power is getting to the compressor does not mean that power is getting to the motor. Besides the ON/OFF switch that might be in the circuit between the wall plug and the compressor motor is the pressure switch. If the compressor pressure switch has not tripped to allow power to flow through it to the motor, the compressor cannot start.
Unfortunately, if you don’t have a poke probe or a multi-meter you will have a difficult time doing the next check.
Comments or questions are welcome. Please use the comment box below. More information about compressor starting problems is available on the next page. Follow the link… more reasons why an air compressor will not start.