Electric motor troubleshooting

550Doug · Jan 9, 2014

I have a small manlift that operated fine this past summer but not now. It has an electric motor that powers a hydraulic pump and a transformer setup that reverses the electric motor for the up or down movement of the hyd cylinder. The motor will only slightly hum right now but will not operate.

On the diagram I've labelled a circle as the "Reverser" but I don't know what kind of transformer it is. I have unhooked and cleaned the four connection points but again no change. I believe the yellow Up/Down switch is run on DC and I suspect that's why there is that other small transformer present.
Any ideas on how to verify if the main "Reverser" is the problem? Maybe I should pull the motor??
Thanks

LarrySTN · Jan 9, 2014

I would check the capacitor on the motor.

glennster · Jan 9, 2014

looks like a lot of corrosion on the tire terminals and connections. first thing i would do is take each one off and clean it bright and shiny one at a time.

buickanddeere · Jan 9, 2014

Usually lifts don't run the motor for "down" but lower on gravity instead.
I would agree that a start capacitor, open starter switch, starter contactor or open start winding are suspects.
If the motor really does reverse then the start winding polarity will be swapped by the contactor.

JMOR · Jan 9, 2014

I do not know that lift, but her are some observations that "might" help you figure it out: Transformer likely provides low voltage to operate the reversing valve and contactor. Contactor in box that you call "reverser?". Reversing accomplished by control valve at upper right. Pump does not reverse, based on observation of hose-clamped low pressure type suction line that doesn't look like it could support high pressure. As someone else said about the motor, check the capacitor.

Donaldinky · Jan 9, 2014

See if the motor will turn see if the bearing are good. Than
check the caps. There under the hump. Change is the best
way way if don't know how to check them. Than when it
humming hit it with a rubber hammer might be the start switch
is stuck. Just some ideal.

550Doug · Jan 9, 2014

Thanks for the replies folks.
Is it the "hump" that I hit with a rubber hammer to try to jar something loose?
Yes I do need power to lower the unit. I was once on the unit with an electric pole saw and and I managed to stall the saw and it killed the small generator I was using to power BOTH the saw and the manlift. That was scary getting down from 24 feet!!

Steve@Advance · Jan 9, 2014

Yes, it needs power to come down, but only to operate the solenoid valve. The motor only runs to go up. That simplifies everything.

If the motor hums, you're sure it is the motor humming, not the contactor magnet, then the problem is in the motor, or the pump is locked up (not likely). See if the pump/motor will freely turn by hand, if so the problem is in the motor.

Walt Davies · Jan 9, 2014

Check out the outriggers they should have acnicro switch all of
these must be on before the motor will run. Try testing each
switch to see if they are working.
Walt

waltdavies · Jan 9, 2014

Micro switch not acnicro darn spell check.
Walt

Anonymous-0 · Jan 9, 2014

The connection diagram on the motor nameplate shows the connections for cw and ccw rotation. (cw rotation facing shaft wired as shown, ccw rotation by interchanging two terminals (I can't make out the terminal designation in the photo)) So, if indeed the motor reverses to lower, I would check to see you are getting power to those terminals.

37chief · Jan 9, 2014

I would clean all the connections to start with. If the motor is still only humming, See if the motor turns by hand? If so I would give the sniff test. remove the wiring access door, if it smells burned, start looking for another motor. My opinion, for what it's worth. Stan

Paul from MI · Jan 9, 2014

Most likely the start switch in the motor, but could be a bad start winding in the motor, or a bad starting capacitor. Check to see if you are getting full voltage to the motor, if so, the problem is in the motor and a good motor shop can fix it. Hammer technology will most likely result in a new motor.

Geo-TH,In · Jan 9, 2014

What a rusty mess. How did it get that way?

If rust is present outside all the switches, relays, rust will be inside too.

Usually anytime a motor hums, the end switch inside the rusty motor isn't making contact. Start by taking motor apart. If rust on the rotor is touching the stator, motor won't run.

Make sure governor and end switch is rust free and in working order.

It wouldn't surprise me if you don't need to replace the contactor and other components. WHAT A MESS.

Motor says 60 cycle, definately an AC motor. To reverse an AC motor, the wires going to the start windings have to be reversed. Good chance the reversing is done in the up/down switch.

good luck.

jerrybigrig · Jan 9, 2014

Check all the wire connections. Don't assume they are making
good contact because you can see that they are still on their
proper spots . Pull on them w your hand or pliers . ( I know don't
assume)

Electric motor troubleshooting

550Doug

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LarrySTN

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glennster

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buickanddeere

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JMOR

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Donaldinky

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550Doug

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Steve@Advance

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Walt Davies

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waltdavies

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Anonymous-0

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37chief

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Paul from MI

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Geo-TH,In

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jerrybigrig

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