Garage door opener motor working, but chain isn't moving

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Old 05-21-18, 10:01 AM
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Garage door opener motor working, but chain isn't moving

I was adjusting the down travel on my Craftsman 1/2 HP 139.53960SRT, and while testing the travel the door stopped moving while the motor was still operating. I disconnected the door and the motor will operate, but the chain doesn't move. The chain is still on the sprocket on top of the motor housing.

Is the motor shot? If not, is the required servicing DIY-able? This garage door opener is at least 20 years old (not sure of exact age, but it was installed by prior homeowner). If the motor is shot, if it's not DIY-able, should I bother having it repaired or just buy a new garage door opener?
 
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Old 05-21-18, 10:20 AM
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You've likely stripped the nylon gears in the motor housing. Pretty simple replacement with common hand tools. Probably takes about an hour for a 1st timer. If you take the cover off, likely you'll see a bunch of white shavings in the housing.

Kit's are available through garage door repair stores, Sears, Amazon, Ebay. I suggest using a reputable company on either of the last two. It will be cheaper and they often have lots of information/videos on the storefront sites. Since you have a Craftsman (made by Chamberlain I believe), it might be easier to order through Sears. Get both gears, though only one may appear worn.

All this is based on you having the sensors to detect blockages in front of the door. If you don't have those, then by all means you should upgrade to a newer screw or belt drive opener. HD and elsewhere have some good prices right now due to the upcoming Memorial Day. $160-180 for a belt drive from Genie or Chamberlain. My personal choice is Genie as I have had very good success dealing with the company. (Of course they are located near my hometown...so I have a hook.)
 
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Old 05-21-18, 07:09 PM
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Thanks for the info!

Originally Posted by Gunguy45 View Post
You've likely stripped the nylon gears in the motor housing. Pretty simple replacement with common hand tools. Probably takes about an hour for a 1st timer. If you take the cover off, likely you'll see a bunch of white shavings in the housing.

Kit's are available through garage door repair stores, Sears, Amazon, Ebay. I suggest using a reputable company on either of the last two. It will be cheaper and they often have lots of information/videos on the storefront sites. Since you have a Craftsman (made by Chamberlain I believe), it might be easier to order through Sears. Get both gears, though only one may appear worn.
You're probably right. I noticed when I was adjusting the down limit screw that there was a bunch of white plastic shavings around the limit screw holes.

I'll take the opener down and open it up and see what's what. I'll check out some videos on this.

Originally Posted by Gunguy45 View Post
All this is based on you having the sensors to detect blockages in front of the door.
Yeah, there are sensors near the ground on either side of the door. So if I can repair this one relatively cheaply and get a few more years, I'll go with that. Give the companies some time to perfect the "smart"/IOT openers so that they are very reliable and very hack resistant.
 
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Old 06-02-18, 06:55 AM
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As expected, the large plastic gear was totally shredded. There were plastic shavings covering everything inside the opener.

I bought one of those gear and sprocket kits (the gear and sprocket assembly comes assembled, so you just have to drop it in). The kit also includes the worm gear and washers, bushing and lockring for it.

Replacing the worm gear was a hassle because the motor shaft bushing was stuck onto the shaft. I had to hammer the end of the shaft very hard to get the bushing to move. At that point the end of the shaft was peened, so even though the bushing was loosened, it couldn't slide off. I ended up removing the motor mounting bracket and motor. Once I got it down, I used a Dremel sanding drum to carefully reshape the end of the shaft - you don't want to take off too much material because the spinning cap for the RPM unit sits on the end of the shaft. Alternatively, if you find that the motor shaft bushing is stuck, you can skip replacing the worm gear if it doesn't look too bad, or you can take the motor and bracket down, and carefully cut off the bushing using a Dremel and cutting wheel.

Other than that, it was a straightforward job. Opener runs great now.

For anyone undertaking this, I'd suggest the following tools: cordless driver with 1/4" extension and SAE sockets, a 1/4" drive ratchet, a 1/2" ratcheting wrench (for the nut at the end of the chain). SAE hex wrench (I think 1/8") for lockring if replacing the wormgear (though check your specific model, some use a roll pin, so you'll need a roll pin punch instead). You can probably do the job without all these tools, but when you're standing on a ladder working overhead in a tight space, the right tools will make the job a lot easier.

The gear and sprocket kit also includes a bushing for this assembly that sits in the motor mounting bracket. The bushing is a press fit and if your unit is very old, you'll need a vise (requires removing the motor and bracket, which is relatively easy to do) or c-clamp + large socket (think axle nut sized socket) to press it out and press in the new bushing. If the bushing is in good shape, no need to bother with this. Mine was pitted, so I replaced it.

There are a lot of Youtube videos on replacing the gear, but the best one I found is this 4-part video: https://www.youtube.com/watch?v=nmZlYQAZmLg

Despite the low production quality, this video conveys more details than any of the others I've seen.
 
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Old 06-02-18, 08:02 AM
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The rebuilding process is much easier when you lower the unit. I leave the bar connected at the opening and drop the motor unit allowing it to sit on a short step ladder.
 
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Old 06-02-18, 09:05 AM
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Originally Posted by PJmax View Post
The rebuilding process is much easier when you lower the unit. I leave the bar connected at the opening and drop the motor unit allowing it to sit on a short step ladder.
For sure.

In my case, whoever installed the opener made such a convoluted mess of how they ran the wires from the opener to the switch, it was easier to remove the motor and motor mounting bracket than it was to lower the opener housing.

For anyone looking to do the same, the motor has 3 wires coming out - disconnect the two to the capacitor and the one wire to the power. Then it's just 4 screws to loosen the motor mounting bracket from the housing.
 
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