backend motor problem

[jandlcox]

I have a AO Smith backend motor just rebuilt. Hook it up on the bench and it runs great, put it on the machine and it just sits and hums. Plug it in with just a cord with connectors still dont work. Carried it back with same cord and hook it up on the bench sounds great. Take it back to machine bolt it down hums. Tried to take it off machine and put it on floor next to machine plug it in sounds and runs great. Sounds like a bad ground somewhere where would I start looking for it.

Thanks

[kevin]

Re: backend motor problem

Will another motor run on the Machine? Did you check to see if your getting the proper voltage to the motor threw the machine motor plug?

Just some thoughts. Good Luck! [img]/content/btubb/images/%%GRAEMLIN_URL%%/cool.gif[/img]

[kevin]

Re: backend motor problem

Originally posted by kevin:
Will another motor run on the Machine? Did you check to see if your getting the proper voltage to the motor threw the machine motor plug?

Just some thoughts. Good Luck! [img]/content/btubb/images/%%GRAEMLIN_URL%%/cool.gif[/img]

<font size="2" face="Verdana, Helvetica, sans-serif">Sorry I did not read your post properly.
Did you re-install all the belts and distributer drive shaft? Is something binding the motor?

[sbsmoss]

Re: backend motor problem

with the motor on the work bench put a wire on a screw on the head then touch conduit if the motor hums it has a internal short. be careful if it does because it will have 110volts from the head to ground.

[Ed Fox]

Re: backend motor problem

Since it only starts with out a load sounds like a bad switch adjustment or a bad start winding to me.

Charlie [img]/content/btubb/images/%%GRAEMLIN_URL%%/smile.gif[/img]

[Rep]

Re: backend motor problem

I'm with Ed here, probably bad start windings. We get that a lot, motors that are totally fine on the bench but wont pull a load. Plenty of times its the start windings

[Lampie]

Re: backend motor problem

On an ohm meter you should not have any reading(s) between one of the wires an the outside of the motor/stator, check that first.

[jandlcox]

Re: backend motor problem

There is not a load on the motor. I bolt the motor up and make sure no belts are connected. Plug it in with the machine plug and it hums. Plug it in with my test plug into an outlet on the wall it hums. Take the motor of the machine, put it on the ground use the same test plug and same outlet works fine.

[Lampie]

Re: backend motor problem

Put a ground wire on the casting if the motor is on the ground [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img] [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img] I think it will hum too!
There must be a short to ground somewhere(inside the motor)!
You realy need an ohm meter and check the resistance between the wires and the outside of the motor(this should be infinite/endless-not sure about the correct expression in English).
If you put the motor on the machine it will be grounded, on the workbench and on the floor it's not.
If you are lucky it's one of the wires you can see coming out of the stator or near the capicitor, if you are not lucky it's somewhere inside the coils, the stator will have to be rewinded(new coils).
I've had the same problem even with a new stator(well, it came in and was made on a mondaymorning [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img] ).
Good luck

[LancerLanesMech]

Re: backend motor problem

Sounds haunted to me [img]/content/btubb/images/%%GRAEMLIN_URL%%/confused.gif[/img] [img]/content/btubb/images/%%GRAEMLIN_URL%%/confused.gif[/img]

[AmfPro]

Re: backend motor problem

Sounds to me like bad C1 pins. Try switching chassis with next lane. If still same, check C1 harness connectors and terminal block inside backend control box. We bypassed the terminal block years ago because of bad connection continuity between the C1 harness and the pit motor plug. Could also be a worn out motor plug on the machine also

[Mike Stalker]

Re: backend motor problem

Here are my 2 cents.

First if I read your post correctly, your stator and gearbox are indeed one when you take it to the bench and then try it on the machine.

If so, as Ed has figured out, you have no load on the bench, therefore a weak capacitor will still start a motor.

You have four possible suspects in your start circuit. Start winding, start capacitor, centrifugal mech, and your switch board.

Because your motor starts on the bench, you have elininated the cent mech, switch board, and start winding. You obviously have a weak capacitor. A borderline cap will start a motor with no load on it.

Put the motor on the machine but do not hook up your belts and see if it runs, you can figure out the rest from here.

Mike

[John_Galt]

Re: backend motor problem

Look, do you have 117 VAC out of your BE plug? If yes, then replace the capacitor and switch. If no, replace C1 45W pin and socket.
C

[E300]

Re: backend motor problem

Ok, I think I'm missing something here, but isn't the part (centrifugal mechanism) that throws the switch from the starter winding to the run winding on the armature . And is not the same one on the bench. try taking the bell cap off the stater and putting just the bell on the gearbox armature that doesn't run. see how the switch lines up with the cent. mech. acualy move the mechanism back and forth to see if it makes contact and then doesn't. If thats ok u could check the bearing and how thats sitting in the bell and if its good or not. after going this far and still no good. swap bench grearbox with defect.
PS still new to this, so go easy on me if I made stupid statements.