When the air compressor will not re-start, the compressor troubleshooting process is similar to that of when your air compressor won’t start in the first place.
Except, that you know for sure your air compressor will run as it just did that. But now, that the pressure in the tank has reached cut out and the air compressor stopped, the compressor will not re-start when air is used.
Since the compressor was just running, you can typically pass on checking the power supply. The compressor is trying to re-start, which means that power is still getting to the motor circuit and if it was running before and the compressor tank pressure reached cut out and the compressor stopped normally, likely the power supply is OK.
Compressor motor too hot?
If you’ve run the air compressor for a long time in a single session, totally ignoring the fact that many air compressors have a duty cycle and need time to cool down every ten minutes or so, it may be that the motor has overheated.
Compressor motors often have a thermal switch in them which trips open and stops the power to the compressor motor if it gets too hot. If you’ve been abusing your compressor a bit in terms of how long you’ve had it running, see the page on this site about duty cycle for some tips.
Compressor trying to start!
If the compressor is trying to start and cannot, there are a number of conditions that will cause this.
One of the easiest is to determine if the compressor unloader is working. I won’t go into details about what it is and does here, as it’s covered in great detail on the Unloader Valve page on this site. Check that out if you don’t know what the unloader valve is. Suffice to say that if the unloader isn’t working your compressor may not restart, though it wants to.
If you pull the power cord and open the tank drain and let the tank empty completely, you are emulating what the unloader valve does. Once the tank is empty, make sure to close the drain and plug the compressor back in.
If it starts easily now, then you can be pretty sure that the compressor unloader valve isn’t working properly, and you need to correct that. Again, see the Unloader Valve page for details.
In the simplest of terms, a start capacitor boosts the compressor motor to help get it going.
If the start cap is weak, or failing, though it tries to, your air compressor motor may not re-start, even though it had been working fine just a short time before.
Checking the start capacitor requires a bit (OK, a lot) of fiddly work, including removing it from the motor side without shocking yourself, and using a multi-meter to check it. Lots of info on this site about how to do that. So check out those pages too.
Your air compressor still not re-starting? No idea why? Then send in your question and tell us what you have already checked, will you?