Why does my garage door opener just hum when I try to close the door?
I have a Sears Craftsman garage door opener, model 139.53644SRT. When I try to use it, it makes 2 short (a few seconds) hums, and nothing happens. The light works. I have tried the remote, wall switch, and code panel. Same results. The last time that it worked, I used the remote, and it opened without problems. A few seconds later, when I use the wall switch to close it, I got the hums and nothing else.
Expert
Maestro
Typically, once one of the components has failed you will not hear any humming and if the door is jammed there will be some jerking as the motor tries to engage so if there is no movement at all the most likely problem is the motor/lift assembly itself is jammed.
As components wear it is possible for the Worm Gear and Drive Gear to move slightly as they transfer force from the motor to the lift mechanism. If that play is enough the Limit Switch, which also runs off the Worm Gear assembly, can skip gears until it is out of time. Then the door could lift too far and jam against lift assembly.
There are upper and lower limit screws that you can see on your overhead opener unit. If you remove the covers you will see that those screws connect to an assembly with 3 threaded shafts. The outside shafts are the upper and lower limit screws and the center one connects to the Worm Gear assembly. As the center shaft moves a small metal tab attached to it connects to another tab on the upper or lower limit to tell the opener it is at the limit for door travel. If the timing is off by enough you may even see a gap between the tabs on the center screw shaft and the upper limit screw shaft.
If the lift assembly is jammed it most likely will need to be manually reset into position and if the limit switch is off then you may need to replace the Worm Gear assembly as well. If everything looks okay there then there could be a problem with the motor itself or the Logic/Control board. At that stage you may want to consult a professional as the voltage can be high, the components are quite costly, and it is easy to damage the board if tested incorrectly.
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