Pump motor start capacitor

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  #1  
Old 11-01-10, 07:38 AM
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Pump motor start capacitor

Not sure if this is the right forum, but I'll try...

My spa pump stopped working and so, as usual, my first step was to take everything apart. I guessed it was a bad electrical connection, so checked everything, and nothing looked amiss. The pump has both a start capacitor and a run capacitor, and both looked fine. I put it back together again and everything worked. Magic, I thought. But it only lasted a day, and then the motor wouldn't restart after cycling off. My guess then was the start capacitor, so I wrapped a string around the spindle and gave a yank, and the motor started working again. Runs fine now, but if I let it cycle off, it won't start up again unless I do the pull start.

My question: does that definitely mean it's the start capacitor? I don't want to have to drain the spa again to fix it, unless I know for sure what the problem is.
 
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  #2  
Old 11-03-10, 04:52 PM
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Kill the power and remove the cover of the cap. If you have a decent meter, it may have a cap tester. Otherwise, using an ohm meter, pull the leads off the cap and put the ohm meter across the cap. If the resistance rises steadily and after a minute reads "OL", then the cap has susessfuly charged and it 'might' be okay. If it reads 1 ohm or less, or anything other than a rising resistance, then the cap is shorted. Look for bulges around the cap or some bleeding dielectric juice. 90% of the start or filter caps that i've measured as bad will have some physical appearance of being NFG.

However, you also might have a bad centrifigal switch. The start cap is in circuit until several revolutions of the motor occur, and then a switch, at the opposite end of shaft, opens contacts to the start cap and transfers current to the run winding and/or run cap. If the switch is NOT disengaging when the motor stops, then you could be trying to start the motor without that start cap and thus not shifting the current phase necessary to turn that motor under load.

Put your volt meter on the load side of the start cap while calling for the motor to run. Put one lead on the cap and the other lead on the other phase of the 240 (or the neutral if it's 120V). If you don't get 240 when starting then your cap might be shot. Then put the lead on the line side of the cap. If you still don't get the 240, then your switch is hung up. Take the motor out and clean the switch or replace springs if they're broken.

You did good by trying to start it by hand. That narrowed it down.

Be careful! Caps store a nice little jolt if you cross them!

For grins, make sure you have 240 across the to wires going to the motor. I've seen contactors with one bad relay contact too and they will close when tapped or you supply a push with spinning the motor.
 
  #3  
Old 11-04-10, 03:50 AM
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Thanks for the details on how to test it. My strategy for repairing stuff is to open it up, and usually broken things will be obvious. I knew that most caps looked bulging if they are bad, and this one didn't, so I took it in to a shop for testing. They said t was fine, and told me it was probably the switch. But the switch looked fine, springs were nice and springy. And I was then officially out of my DIY depth. So the motor is sitting in the shop where I am paying someone to do the work for me. I hate that, but sometimes that's got to be the next step.
 
  #4  
Old 11-08-10, 01:28 PM
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If the cap is good, then you may have an open start winding.
 
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