Clicking Air Compressor

Maybe you haven’t used it for a while, you turn on or plug your air compressor in, and all you get is a clicking air compressor. What’s gone wrong?

Difficult as it may seem, it is first necessary to determine where the clicking is coming from on your air compressor.

Typically, the sources and the solutions of a clicking air compressor are the compressor pressure switch, or the motor itself.

Clicking Pressure Switch On Compressor

If you have an air compressor that contains a pressure switch with contacts inside it, perhaps one similar to the photo below, in order for the pressure switch to transmit power to the motor circuit, the points have to touch firmly.

compressor pressure switch with unloaderThe point movement inside the base of the pressure switch is controlled by springs and, typically, a diaphragm placed in such a way as it reacts to the pressure inside the compressor tank. The tank air pressure pushes on the diaphragm and that pushes or releases the springs to which are connected the electrical points.

If the pressure switch diaphragm has a split or tear that will prevent it from cycling properly, and the ensuing depressing and releasing of the springs as air escapes through the diaphragm tear can open and close the points and that may be audible as a clicking sound.

If the compressor is working properly however (other than a failing pressure switch) most likely the compressor would react to this cycling of the pressure switch by turning on and off frequently, and not at the normal cut in or cut out pressure levels.

Worn Pressure Switch Points Click

The points inside the pressure switch can become contaminated or corroded over time. If that has happened in your pressure switch, the points may click as they try to meet, and if badly corroded then power cannot cross the points, even though they may be chattering. Your compressor will not start, and your pressure switch will be emanating the clicking sound you hear.

If either of the two scenarios above are happening it’s time to replace the pressure switch.

Compressor Motor Has A Centrifugal Switch

This next image is an example of a typical electric motor centrifugal switch. You can see how the switch would mount on the motor shaft through the center opening. The two counterweights – top left and bottom right – would slowly open outwards as the shaft speed increased  to the point where the centrifugal switch would trip.

air compressor motor centrifugal switch - fix-my-compressor.comThe air compressor motor centrifugal switch is found on split-phase (single phase) motors which make up a significant number of compressor motors. Odds are good that your compressor motor is a split-phase and has a centrifugal switch.

The split phase motor has two windings, a start winding and a run winding. The start winding is used very briefly on compressor motor startup and they are disconnected and the motor shifts to the run windings as the motor comes up to speed.

How can you tell if your motor has a centrifugal switch? When your air compressor was starting and working properly, then when you have turned your compressor off, or when it shut down on normal high pressure cut out, the motor would slow, and when the shaft speed became slow enough, would hear the click as the centrifugal switch disengages.

If it is the centrifugal switch that has failed, your motor start windings may not be energized properly, or, in time if the centrifugal switch stays energized the run windings may overheat and burn.

If that has happened, then the air compressor will not start, but then, you shouldn’t hear a clicking sound when the compressor is trying to start.

Clicking Air Compressor

Back to the beginning, then.

If, when the compressor tries to start, all you are hearing is a clicking sound, closely monitor the air compressor to try to determine where the sound is coming from.

Please use the comment box below to advise from where, on your air compressor, you are hearing the clicking noise when your air compressor tries to start. Also note any other sounds or conditions from the compressor as the start sequence fails. We will attempt to help further when we know the source of the sound and the other air compressor conditions.


  1. Hi, i have an fiac single phase compressor, with a 2.2kw 3hp 2800 motor, the motor start fine but as soon as its under load it starts to slow and struggle, i have pulled the motor and the winmdings look fine, i can see no centrifugal switch. It has 2 capacitors that i can only assume are start and run, one is a slightly smaller diameter 55uf, and the other a fatter 65uf, could one of these be the problem and how do i tell which is the start and run?

    • Tough one. If this were our compressor we would test both caps to see which has failed. We would also email Fiac directly, and, when providing the model number of the Fiac air compressor we had, ask which cap is which.

      FIAC Air Compressors S.p.A.
      Via Vizzano, 23 – 40037 Pontecchio Marconi – Bologna (Italy)
      Tel: +39 051 6786811 – Fax: +39 051 845261 e-mail:

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