How to Diagnose Problems With an Air Compressor

A screwdriver is the only tool required to troubleshoot most compressor issues.
A screwdriver is the only tool required to troubleshoot most compressor issues. (Image: screwdriver image by hazel proudlove from

There are three main troubleshooting tracks to follow when trying to diagnose problems with air compressors. The first is ensuring power so that the compressor motor will come on. Once this has been taken care of, the next thing is to make sure that the compressor will hold pressure. Last but not least is establishing a controlled flow of air so that tools and machinery will operate at their best.

Things You'll Need

  • Screwdriver
  • Small lamp
  • Spray bottle with soapy water
  • Wrench
  • Locking pliers
  • Pneumatic tool oil

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Compressors That Won't Turn On

Turn the power switch to the on position. Track back the power cord to its source. Reconnect any loose cords. Check the outlet and adjust the plug to ensure it is plugged in properly. Locate the power reset breaker on the compressor. This is a small black or red button, typically located on the rear of the compressor motor. Depress this button to reset. If power is restored, continue working normally. If not, proceed to the next step.

Locate the circuit breaker box and check to see that no breakers have been tripped. Look for switches with a red square in the indicator. Flip the breaker all the way to the off position and back to on to reset. Test the compressor again. If power is restored, return to work. If not, continue to the next step.

Test the outlet with a working radio or small lamp. Plug the appliance into the outlet and turn it on. If it is working, the problem is either with the compressor or the cords. Remove any extension cords and plug the compressor directly into the outlet and turn it on. Return to work if power is restored, or continue to the next step if not.

Pull the release valve on the compressor to release the pressure to engage the lower limiter control switch. The release valve is a plastic-and-metal valve with a pull ring in the end. The limiter switch kicks the motor on when the pressure is lower than a certain point and kicks it off when the desired pressure is reached. Compressors that do not respond to these steps may require professional servicing.

Compressors That Won't Hold a Charge

Disconnect tools and hoses and turn the compressor on. Spray soapy water from a spray bottle around the fittings on the compressor motor and tank. Look for bubbles to indicate a leaky fitting. Tighten leaky fittings with a wrench by turning them clockwise.

Reconnect air hoses and run a hand along them, feeling for escaping air. Replace hoses that have ruptured rather than attempting repairs. Hoses are inexpensive, difficult to repair, and a bursting hose can cause injury.

Run the compressor and loosen the bleeder valve on the bottom of the compressor tank. Use locking pliers to turn the valve counterclockwise. This will allow air to force out any condensation that is in the tank. Keep the valve open until the air coming out is dry, then tighten the valve closed, turning it clockwise.

Inconsistent Air Flow

Check all stop cocks on the compressor outlet and along the air line. Turn them to the full open position. Oil the tool by placing a few drops of pneumatic tool oil into the fitting where it connects to the air hose. Test to see if tool operates correctly. If not, continue.

Remove the cover to expose the limiter switch control screws. The cover is vented and typically sits atop the compressor motor. Use a screwdriver to remove the screws and lift the cover from the compressor. The upper and lower limiter switch are located on top of the motor, near the air outlet. The screw nearest the back is typically the upper limit screw.

Turn the upper limit control screw clockwise to increase the pressure required to turn the compressor off. This will raise the pressure in the tank. Turn the lower limiter control switch clockwise to raise the pressure at which the compressor kicks on. This will help to maintain a higher pressure. Adjust these as needed to get a good, steady working pressure. Replace the cover, and thread the mounting screws back into their holes. Tighten with a screwdriver.


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