Start Capacitors and electric motors

[jacwjames]

I'll admit, I am an amateur electrician.  I do have some back ground, college courses for my engineering degree, which pretty much just makes me dangerous.  I worked in mining which uses high voltage machinery and I learned to have a safe appreciation of it's potential. 

But I'm not afraid to tear into something when it breaks.  So I had a motor with capacitor that quite working, it would only hum.  So I knew enough to remove the capacitor, short out the terminals to dissipate the stored energy, and test.  It tested bad so I bought a new one.  But that didn't fix the problem

So to Youtube I went and started searching how to test the motor.  Most talked about testing the windings etc.  But then I stumbled onto one that showed how to check the centrifugal type switch that works with the capacitor, basically allowing the stored energy to "help" the motor start but as it starts the switch drops out isolating the capacitor. 

So I tore into the motor, sure enough I found the switch and really couldn't find a problem but I did take some emery cloth and clean the contacts.  Put everything back together and it worked.   A replacement motor like this is pretty expensive, probably $750 or more if I could even find one.  So I'm a happy camper. 

So if you have a motor that fails you might look to see if it may have a centrifugal type switch, it might save you some money. 

[Joe Lee]

Thanks for taking the time to write this up and share!

[Cubflyer]

Actually Jim the motors with the 'centrifugal switch' have 'start windings' that are energized by the switch (along with the capacitor) to get it running, then drops out of the circuit in the 'run' mode... quite common.... my shop air compressor has failed in this manner... 

Good that you brought this to our attention.

Ken

 

[LakeBob]

Thanks for sharing this. What application is the motor used in?

[PAPARO]

Thanks for sharing.  I’m getting so many great tips on all sorts of “Issues “.

Great site! 

[Notn2bars]

Thanks for sharing Jim, your posts are always on target and so valuable for us who do as much as our own work as possible.  God Bless, Ed & Sylvia

[jacwjames]

To All.

I post something like this hoping I might be able to help someone else.  I know others do the same thing. 

Although this was not RV related this type of thing may apply to other applications, the shop compressor is a good example. 

[Guest Ray Davis]

Jim, IMHO that's good stuff.  I lived most of my life repairing & patching things.  Early on because I couldn't afford new motors etc.  Now it's mostly because I don't like to throw away what may just need a little fixing, plus I'm still cheap.  I take satisfication in making things work.  So keep it coming, I always enjoy your posts.

[SteveB]

Well thanks Jim, my HydroHot motor is acting up.  Hums pretty good until I tap it with my hand and then starts. This is good information to know before I do the teardown.

[Guest Ray Davis]

6 hours ago, SteveB said:

Well thanks Jim, my HydroHot motor is acting up.  Hums pretty good until I tap it with my hand and then starts. This is good information to know before I do the teardown.

The HydroHot motor is probably like my AquaHot motor and it's different from the ones mentioned above.  Those were AC current motors and ours are 12 volt DC motors.

My guess is you probably need new bearings or it is dragging / rubbing on something.   Another possibility could be low voltage.

[SteveB]

Hi Ray, I just saw your post and thank you for commenting. The voltage levels were checked and are where they should be. I ordered a 5 year rebuild kit from John Carrillo which has the bearings as you suggest and an Aqua/Hydro-Hot motor as well....although I like the idea Jim had with the emery cloth.