Asked by: Yone Neundorf
Asked in category: home and garden, indoor environmental quality
Last Updated: 7th Feb 2023

Is a bad capacitor preventing a motor's starting?

FAQs about Electric Motor Start Capacitor and Run Capacitor. The motor might fail to start if one or both of the run and start capacitors is defective. If this happens, the motor will stop running and hum. A bad compressor motor is suspected if the circuit breaker trips, or the fuse blows during compressor start-up.

A bad run capacitor will also affect the motor's ability to start.

You can also look for signs that indicate a problem with the capacitor in a motor. A motor with a short-circuited cap will often start and run but have lower starting torque and full-load rpms than normal.

Why does a motor require a start capacitor? A capacitor connected in series with the secondary winding creates a magnetic field that is lower than the primary winding's. This creates a start torque, and the motor begins to turn. Start capacitors are capacitors that enable a motor's rotation to begin.

The same goes for a motor starter capacitor.

A start capacitor is required for many single-phase compressors. Sometimes, these capacitors can fail and cause a compressor not to start. Overheating can be a primary reason for a failing start capacitor. Failure of a start capacitor will occur if it is left in the circuit for too long.

What happens if the run capacitor is damaged?

A hard starting is the most common problem bad capacitors can create. Most cases of capacitor failure, including damage to the capacitor or loss of charge, will require replacement.