Difference between a start capacitor and a run capacitor?
My rooftop unit's fan runs fine but sometimes the compressor won't come on. I hear a faint click but it won't engage and doesn't blow cold. Would this be a start or run capacitor issue?
Forum Discussion
In a single-phase induction motor, the phase-shifting property of the start capacitor is used to create a rotating magnetic field to get the motor turning from a dead stop. Once the motor is turning it is not needed and in most motors is disconnected. The run capacitor counteracts the inductive phase shift caused by the stator winding(s), providing power factor correction. The motor will run without it, running hotter and using more power.
If the motor never starts turning, the start capacitor would be the suspect. Of course, it's impossible to see this inside the compressor, and it could be a problem other than one of the capacitors, as suggested in the first response. Could even be a locked-up compressor.
If the motor never starts turning, the start capacitor would be the suspect. Of course, it's impossible to see this inside the compressor, and it could be a problem other than one of the capacitors, as suggested in the first response. Could even be a locked-up compressor.
