LiftMaster Door Operator

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caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
Does anyone here have any experience with the Liftmaster Commercial Door operator, model MJ-5011? It's supposed to be an indoor roll-up door opener like for a warehouse, but they are very commonly used to operate outdoor chain-drive rolling gates here in Puerto Rico. We use one to operate our rolling gate to our house and it is very erratic. Anyone here have any experience with this unit?
 

kwired

Electron manager
Location
NE Nebraska
Describe what is happening that is erratic.

If it only moves the gate so far then stops or even reverses, might be too much force needed to move the gate and it is doing what it is supposed to do instead of breaking something from too much force.

Well operating and well adjusted overhead door shouldn't take a lot of force to open or close, which is what this thing was designed to operate.
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
It's a rolling gate on ballbearing wheels running on an inverted angle iron track. It is completely smooth with no binds anywhere. Usually the motor refuses to turn even though it's getting the signal from the remote. You can hear switches and relays clicking and it's getting power, you can hear it hum, but it's pulling over 8amps while stalled, according to my meter, rather than the ~4amps it draws when running. I can't see anything wrong, and I've tried changing the starting capacitor and that did not solve this problem. Moreover, it's very erratic...the problem comes and goes seemingly without any pattern. This is truly a mystery and I welcome any ideas here that fit the symptoms.
 

kwired

Electron manager
Location
NE Nebraska
Such units have a "reversing contactor" to control the motor. If it is intermittent kind of thing probably dirt/debris/dead insect(s) interfering with one pole of a contactor, so you end up with main or aux motor winding being energized but not both. Simply blowing contactor out with compressed air possibly fixes this if that is what is going on.
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
Thanks for the replies, folks. The starting capacitor was replaced in our original unit and it ran even worse, more stalls, so I put the original back in. The new replacement unit is only a year old, all the switches have their contacts inside sealed plastic housings....you can't see the actual contacts, just the actuating lever outside the housing, so there's nothing to blow clean. This is a total mystery, it comes and goes, making troubleshooting extremely difficult, because as Murphy's axiom says, it will only do it when you don't have time to mess with it. And I don't think it has a centrifugal start switch. It starts by what seems to be a completed circuit from the radio receiver when it gets the command.
 

McLintock

Senior Member
Location
USA
Occupation
Electrician
In my experience , I would check to see if the clutch needs to be adjusted, I would check if you are getting interference with another opener or radio signal, if those don’t work I would replace the unit, as I found out it saves time and most the time money because your not throwing parts at it. Liftmaster CC sucks too you can spend hours on the phone and not get anything fixed


“ shoot low boys their riding shetland ponies”
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Since it’s humming, but not turning, and everything is free, I would say it’s the start circuit, I assume it is single phase, so it will have either a centrifugal switch on the motor shaft (inside the motor housing) or a current relay that opens the start winding. Is the capacitor piggybacked on the motor? Or mounted in the control cabinet?
 

kwired

Electron manager
Location
NE Nebraska
Since it’s humming, but not turning, and everything is free, I would say it’s the start circuit, I assume it is single phase, so it will have either a centrifugal switch on the motor shaft (inside the motor housing) or a current relay that opens the start winding. Is the capacitor piggybacked on the motor? Or mounted in the control cabinet?
Some these things don't have a start capacitor nor a centrifugal switch, they are just a reversible PSC motor. I have had trouble calls before where flies (or other insects) get into the contactor and cause failure to make contact, either on a power pole or on aux contacts for control circuit. I'd probably check that out first since it is pretty easy to do.

This presuming it is more of a commercial door operator. residential ones don't always have the same type of contactor and may have more of a PCB relay that probably is sealed enough this won't be a problem
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Some these things don't have a start capacitor nor a centrifugal switch, they are just a reversible PSC motor. I have had trouble calls before where flies (or other insects) get into the contactor and cause failure to make contact, either on a power pole or on aux contacts for control circuit. I'd probably check that out first since it is pretty easy to do.

This presuming it is more of a commercial door operator. residential ones don't always have the same type of contactor and may have more of a PCB relay that probably is sealed enough this won't be a problem
Looked up the wiring diagram, does have a capacitor, probably is a PSC motor like you said. Looks like solid state control, and the motor IMG_0932.PNG terminates to a pc board, so it is controlling the reversing functions.
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
Looked up the wiring diagram, does have a capacitor, probably is a PSC motor like you said. Looks like solid state control, and the motor View attachment 2553050 terminates to a pc board, so it is controlling the reversing functions.
I think that's the schematic for my unit. Attached is what I have. It's an MJ-5011 model MT. This current unit is a replacement for the identical unit that was also acting erratically for years. It would get 'stuck' open and not close, or vice versa. A little shove in right direction would usually get it to roll and then it might not do that again for weeks, or maybe the next day. Totally erratic. So we replaced it with a brand new unit of the same model and the new one is doing similar things...it 'stalls,' refusing to roll either open or closed, it can happen in either position, and it also has another trick: it will start to close. stop halfway, another press of the remote and it will close another 2' or so and stop again, and another press of the remote and it will reverse itself and go back to fully open! The only PC board I see in there is in the remote receiver, which may be emitting spurious signals. How would I check it? It looks like there are three connections from the radio receiver to the motor control section, labeled R1, R2 & R3. I've seen the installer short two of these and the gate opens (or closes, as is the case). Regarding the starting capacitor, I had changed that on my original unit and it made no difference, in fact I'd say it worked more erratically than with the original. so I put the original back in. The current unit was manufactured just over a year ago, Feb 2019, so I doubt the starting capacitor is the problem. Whatcha think? And thanks for your input, everyone.
 

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caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
Since it’s humming, but not turning, and everything is free, I would say it’s the start circuit, I assume it is single phase, so it will have either a centrifugal switch on the motor shaft (inside the motor housing) or a current relay that opens the start winding. Is the capacitor piggybacked on the motor? Or mounted in the control cabinet?
The capacitor is a separate piece, inside the control box. I changed it on my original unit which was doing the same 'stall' business, and it didn't improve anything. The current unit is the exact same model, MJ-5011 model MT, but only a year+ out of the factory. I know it's a roll-up door actuator, but here in Puerto Rico these same units are used extensively for rolling gates and the installer says he's never heard of this same issue before and he's installed countless number of these units for rolling gates. I'm up against a very strange problem. Your help is much appreciated. Thanks.
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
Have you checked the voltage drop when the gate is operating? The utility may be supplying low voltage at times, which would explain the erratic behavior.
We are on a fulltime Tesla system and the voltage is pretty constant. I've put a Kill-O-Watt meter on the unit and during normal operation, the unit draws ~4.5 amps, voltage drops from 117 to 112 and slowly climbs up until the gate finishes its operation. When stalled, you can hear the relays click, you can hear the motor hum, the current draw is a ridiculous 8+amps, voltage drops to 103 or so, but the motor does not start turning. A healthy shove in the right direction sometimes gets it to roll. Whatcha think?
 

kwired

Electron manager
Location
NE Nebraska
That is not a capacitor start motor, the two motor windings are identical and the capacitor is placed in series with one winding in one direction and in series with other winding in the other direction.

I'm still leaning with contactor not closing all the proper contacts for some reason (especially if motor hums but doesn't always turn) or something is happening in the control circuit. to essentially issue a "stop" in mid cycle.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
and it also has another trick: it will start to close. stop halfway, another press of the remote and it will close another 2' or so and stop again, and another press of the remote and it will reverse itself and go back to fully open!

Exactly what garage door operators will do if there is some binding of the door or something gets in the way. Many have some kind of switch scheme to sense when the operator is being overloaded or the door jammed but I see no reason that it can't be done by monitoring the motor current. Even though the gate seems to be moving freely, that operator isn't designed for it and it may be having trouble moving it. There is normally an adjustment that sets the sensitivity on the operator.

-Hal
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Have you measured the resistance of the 2 ohm resistor that's in series with the capacitor between main and auxiliary windings of motor to confirm it's close to that value?
 
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