Pump motor issues

[bmtrimp]

Hey all,

I have a pool pump question. My pump will not start and I can't figure out why. Here are my troubleshooting steps. I wonder if anyone has any suggestions.
Pump is wired 240 single phase. The pump acts like its dead. No humming, no nothing. Its been running fine for a day but decided to stop for some reason.
1. Checked breaker- OK
2. Checked power at pump- OK 120 volts from each line.
3. Checked to make sure terminals were making good contact. OK
4. Checked to see if shaft could turn- OK
5. Checked Capacitor- OK I did replace it just to be sure though.
6. Checked resistance between terminals and ground- Infinite OK
7. Checked resistance between load terminals- started at zero but quickly climbed to 3 ohms - OK?
8. Can't find centrifugal switch (its not on the back like others) but would expect the motor to hum if it was this switch. Plus while powered, i turned the shaft to see if it would start. Nope

I really hate to jump to the conclusion that my motor is dead. Did I miss anything?

Thanks!

 

[JamesW]

What's the voltage line to line?

 

[bmtrimp]

It's zero.. like I said when I measure from each post to ground they both read 120 but across the two it's maybe a half volt. I don't know why I didn't check that earlier. I know it should read 240 but now I can't figure it out. Are they out of phase? Is that a thing? Is it reading 120 on each leg because they are connected via the motor so I'm actually reading the same voltage on either line? Maybe bad switch?

 

[JamesW]

Is it reading 120 on each leg because they are connected via the motor so I'm actually reading the same voltage on either line? Maybe bad switch?

Yes, that's the most likely reason.

Probably one leg is not connected back to power. Probably a bad switch or breaker.

If you remove the leads from the motor and check each to ground, you should see one with 120 and one at zero.

 

[bmtrimp]

Turned out to be some corrosion on the crimped terminal connector. Replaced with new wire and terminal and it's running like a champ. Easy fix! It's great to have others to get a fresh look on things. Thanks!

 

[cjpwalker]

Good catch, glad you could get it fixed.

Just a reminder to all, one I remind the guys at work of often - voltage check to ground is for SAFETY only. As a diagnostic practice it can easily send you off into the weeds. You saw 120v to ground on both legs because with the bad connection, both "sides" of the motor were now on the same side of power.

 

[JamesW]

Good job. Thanks for the update.

 

[bmtrimp]

Good advice!