Pump Centrifugal Switch - Further Reading

If a pump does not start the centrifugal switch may be bad. The centrifugal switch puts the start winding and start capacitor in the circuit to give it the extra torque the motor needs to start, then removes them from the circuit when the motor is up to speed.[1]

The centrifugal switch is supposed to take the capacitor and start winding out of the circuit as soon as the motor rpm gets close to full speed. This should happen in about 2 to 3 seconds. If the capacitor is failing after 3 seconds indicates that it is still in the circuit when it should not be. A start capacitor cannot take continuous voltage for more than a few seconds. The continuous voltage will cause the capacitor to fail.

Centrifugal switches are found on some motors. Some motors use a Permanent Split Capacitor and have no centrifugal switch

If the problem is not the centrifugal switch it could be the Pump Capacitors

Pump Centrifugal Switch.jpg

The centrifugal switch has two main components, The pressure plate mechanism mounts on the shaft and is behind the bearing. The electrical and mechanical contacts are mounted to the motor end plate. While putting the end plate back on you have to be certain that you get the mechanical contacts set in correctly, behind the bearing and in contact with the pressure plate.

With the motor powered off the springs are supposed to push the pressure plate towards the bearing. The plate pushes the mechanical contacts - which in turn closes the electrical contacts. With these contacts closed the start windings and the start capacitor will "see power" up as soon as the power is turned on.

Once the motor is turning fast enough the pressure plate drops away from the bearing and the switch opens - leaving only the run windings and the run capacitor in the circuit.[2]


  • Tapping the switch with a screw driver, with power off, may get the pump running for a while. After a few dozen days/cycles and tapping the switch with a screw driver, with power off, the switch may worked reliably for weeks.
  • To access the centrifugal switch turn off the breaker, open the back and look at the centrifugal switch. Try to manually operate the switch and if you find it is binding put a little oil on the pivot points.
  • Check the contacts on the centrifugal switch to make sure that they're clean.
  • The centrifugal switch looks like copper V strips visible at the back

Periodic Maintenance

  • Periodically clean the contacts. You can use an electronic cleaner but I would not use a lubricant on the contacts as it will leave a residue that could make things worse. You can lube the governor hinges but try to keep it away from the contacts.[3]