Pump motor still hums/doesn't start WITH new capacitor, but runs/spins freely...

Walker34 · Nov 9, 2018

I have a Pentair WhisperFlo WF-26 pump. It's about 10 years old. I recently noticed that it wasn't running. Trying to activate it only resulted in a hum, and automatic shut-off after a few seconds. The impeller is clear, and the shaft spins easily. The motor WILL run just fine with a little twist of the shaft at the back.

Replace the start capacitor, right? Wrong! I've tried 2 replacements, and no luck. (I've checked the voltages going to the capacitor while the motor is running, and I can't pick up any readings at all.)

Any ideas?

pabeader · Nov 10, 2018

Could be a stuck clutch. It's the part with the spring and weights. When the motor is off, this clutch connects the capacitor into the motor circuit. As the motor picks up speed, it opens up the circuit to the capacitor, taking it out of the circuit. If it is stuck in the open position, the capacitor isn't able to do it job.

Walker34 · Nov 10, 2018

pabeader said:
Could be a stuck clutch. It's the part with the spring and weights. When the motor is off, this clutch connects the capacitor into the motor circuit. As the motor picks up speed, it opens up the circuit to the capacitor, taking it out of the circuit. If it is stuck in the open position, the capacitor isn't able to do it job.

That makes sense. Unfortunately I can't find an exploded diagram of the motor anywhere. Is this something that can be done with the usual DIY hand tools, or is this a take-it-to-a-repair-shop job?

pabeader · Nov 12, 2018

90% of the time it's just a little tap with a screw driver. Can you post some pics?

Bama Rambler · Nov 12, 2018

Could be corroded contacts or a bent arm on the centrifugal switch. It looks like a V at the back of the motor.

Walker34 · Nov 12, 2018

pabeader said:
90% of the time it's just a little tap with a screw driver. Can you post some pics?

Here's a couple of quick photos. Pentair WhisperFlo WF-26 motor:

Walker34 · Nov 13, 2018

Bama Rambler said:
Could be corroded contacts or a bent arm on the centrifugal switch. It looks like a V at the back of the motor.

It doesn't seem like the Pentair WF-26 has a "V" centrifugal switch like this that I can find, at least by scouring YouTube.

Bama Rambler · Nov 14, 2018

That looks like it's probably a switchless model, which means that the capacitor is a run capacitor. From your description it sounds like a disconnect between the windings and the capacitor. You could pull the terminal block out and see if it's behind there.