My 41A4315-7a Garage door opener Motor does not engage. It just hum sfor a second then stops. I checked the internal gears and they seem fine. The door buzzes for a second then stops. Any Ideas.

Most common failure is internal plastic gear. If we assume that this is the failure i would suggest disconnect the travel engage latch to the non engaged position. Cycle the door and observe if there comes a time that the motor is humming and the chain or latch is not moving. Other than reversing for just a brief moment at the end of travel at no time should the motor hum as turning and the latch feature not move.

What I suspect is happening in the down direction door wants to close and as the gear rotates the gear slips . This repair is not so difficult for the DIY with some mechanic skills and tools. Lots of u-tube showing you how, Parts are available. Confirm the right part for your specific model. Purchase the gear and shaft as an assembly if you not sure about the difficulty. Part prices are all over the map. Shop around. You can buy just the gear a little more difficult to replace.






His 15 minute estimate may be a little optimistic.
Craftsman LiftMaster Garage Door Opener Won Open or Close Fix the Stripped...

Could be stripped gears internally. Take cover off and look. It will be obvious.

If it just hums and not actually run. Then the trolley is jammed against one of the stop bolts.

If motor continues to run but no chain action check for missing chain tooth or cam gear worn.

Remove the cover from the motor unit and check the drive gear. It is a white nylon gear just in front of the motor unit and will be obvious if it is bad. The part number is 41A2817 and is available from any door opener service company. The part will come with instructions.

Hello,

The problem is not the chain, it is the plastic gear in the unit of the liftmaster Garage Door 1/2 Hp.The plastic gear is not engaging, although it sounds like it is working.

You will have to replace it with a new one, then the liftmaster Garage Door 1/2 Hp will be able to open up once again.

Once you open and remove the old gear, Be sure to thread the screws in all the parts before you install them. Pre-threading them once would really help. Secondly, label the wires on the back of the opener before lowering it to the ladder, so you can put them back in their proper place.

Hope this was helpful.
Goodluck
Elect_Comp

Check the door springs and also the drive gear. The gear is a white nylon gear just in front of the motor unit. It will be pretty obvious if it is going bad. The door spring may be broken.

If the humming you hear is the motor running you need to remove the cover and check the drive gear. It is a white nylon gear just in front of the motor. If it is the motor humming but not turning you have a bad start capacitor which is held by a bracket and is next to the motor.

I just had the same problem. Extreme cold, garage door stops working, motor hums, same here. I opened up the my garage door opener(after unplugging it), and found that the wormwheel had a wear spot on it. This is the gear that allows the motor to raise and lower the garage door. Any way, after the wife "sugested" that the door was too heavy to lift, I went and bought a new garage door lifter. But if you are handy dandy with tools, I have seen the wormwheel for sale here. http://www.aaaremotes.com/gearsprocask.html It's the plastic wheel that went bad on me. If I would have found this before buying the garage door opener, I would have got the sprocket assembly. I hope this helps!

It's the gear drive. There are kits online for about $40, if you're semi-handy you can replace it yourself. Search for liftmaster replacement parts.