Garage door opener hums/buzzes twice but door doesn't open

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Old 07-25-17, 08:54 AM
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Garage door opener hums/buzzes twice but door doesn't open

I have a Chamberlain 1/3 HP chain drive, Model 350, Serial No. 3947B01022, 60 Hz, 6.0 Amps. The motor is Westinghouse E322P775

When I press the open button on the wall, the opener buzzes/hums twice but the door doesn't open. I don't think the motor is turning, but I need to check that. I checked the circuit board and everything seems fine. I checked that capacitor with a multimeter and it seems good but I'm not sure I checked it correctly.

Is there some way to power the motor directly to test the motor? The motor has three wires going to it, blue, red and white. I'm not sure how much current to apply and to which wires.
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Old 07-25-17, 12:55 PM
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Lightbulb

I would go the other way- before testing by applying voltage, connect the voltmeter to two of the wires then energize the motor in place. It claims to be a 120V 60Hz 4.5A motor, so you should see which two of the contacts are receiving 120V. Of course, you could also start by disengaging the whole track and just make sure its not a mechanical jam that the motor cannot overcome, if you haven't done that already.... If you connected your voltmeter and you don't see voltage, then try another combination of two. It says AC, so there are not that many combinations- half of what there would be for a DC motor. Your hum might just be the motor straining against too much of a load. On my garage door, I have a pulley that routinely gets caught in the track and needs to be pried out- perhaps you have something similar going on? Best of luck. let us know how it goes.
 
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Old 07-25-17, 01:15 PM
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That's a great idea, I will connect the voltmeter and test the wires leading to the motor while everything is in place. My understanding is that the white AC wire connects to the white motor wire. The black AC power wire connects to the Red side of the capacitor with a red wire also coming from the same side of the capacitor to the motor, the other side of the capacitor has a blue wire going to the motor. The track moves freely, it's not stuck. I will report back in a couple of hours when I get home.
 
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Old 07-25-17, 06:06 PM
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I just checked. I put the multimeter on the blue wire and the white wire, when I hit the door open button, the motor gets 117 volts and the motor hums but does not spin.
I also, put the digital multimeter across the capacitor and it showed a few numbers and then went to zero and stayed at zero.

I presume this means the motor is not working?
 
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Old 07-25-17, 06:38 PM
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99% of the time, the motor will run and move the trolley if the door is disconnected and the button pushed. If it does, you likely have a bad cap (a high failure item). You also need to make sure all gears and pulleys are free to turn. I'm not sure what you mean when you say "track moves freely". How do you know? Did you somehow manually turn the gears and move the trolley assy via the chain? It doesn't take a lot for them to overcome the force of the motor.
 
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Old 07-25-17, 07:12 PM
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If I grab the motor and turn the motor mechanism/shaft, it turns easily, put when the power is going to the motor, motor hums put the motor mechanism/shaft does not turn. I manually turned the gears and moved the trolley assy via the chain.
 
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Old 07-25-17, 08:31 PM
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Gotcha. Most motor repair shops (if you have one) will test for free, just takes them a minute. Of course, I lived near shipyards and industrial areas, so we always had one nearby.

I'm not positive, but seems black and white are your run windings, with red and white being the start windings. Wait, I think I read wrong.

You have 3 wires from the motor. White, blue, and red? SO white and red should be run, white and blue should be start. At least I think so. White and red should be energized when you hit the button til the overload kicks out. White and Blue would just have a momentary burst barely visible unless the start winding is bad. If it were earlier here, I'd go out and check mine (similar opener) but it's about dinner.
 
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Old 07-26-17, 07:36 AM
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The image below is my understanding of how the wiring to the motor with the capacitor. I measured the current coming from the blue wire and the white wire. Maybe I need to also check the red/white wires?
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Old 07-26-17, 01:27 PM
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You should have only 2 wires from the wall switch I believe (if that's what that's meant to represent), but other than that seems right. That switch in the drawing is actually the output of a relay on the board I'm pretty sure. Wish Chamberlain/Liftmaster would make schematics available like Genie does.

Btw...you aren't measuring current, just voltage. Yes, I would check the R-W also. Again, many shops might be able to check your cap as well. Hasn't been mentioned, but even the slightest bulging or leakage means it should be replaced. I'd probably do it if I replaced the motor anyway. Relatively cheap online, buying from a supplier can be 3 times as much.
 
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Old 01-15-18, 08:14 AM
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Hey guys, sorry for the late reply but if anybody in the future stumbles upon this post here's how I solved the same problem:
There was nothing wrong with the capacitor or electric motor. Turns out, there was just a jam somewhere in the chain. I disengaged/disconnected the chain from the garage opener, pressed the button, and voila, no buzzing; the motor spun freely. Greased the worm gear, played around with the chain a bit, reattached it to the gear assembly, made sure the garage would've been in the right position so it wouldn't jam again and got it running again. I don't know if the Michigan cold had anything to do with it, but my Craftsman 139.53535SRT1 came with the house when I moved in 14 years ago.
Good Luck
 
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