Garage door jerks when opening and closing

wow6599January 14, 2009

Last weekend my Garage door wouldn't open at all, just made a humming sound. My husband played around with the opener (Crafstman 1/2 HP 139.53975SRT model) and adjusted something and it started working. Three days later, it started to make this jerking motion when it's opening and closing...any ideas on how to fix this before I call a professional?

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First off make sure the door is functioning properly without the opener. Disconnect it and check operation, including balance.

Beyond that, if it has a chain or belt I'd say something is slipping.

    Bookmark   January 14, 2009 at 8:26AM
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Thanks for the follow up, it opens fine manually, and stays in place. My husband thinks the opener is going out, but from what I've been reading here, that's probably not the cause. How do I find out if something is slipping?

    Bookmark   January 14, 2009 at 6:00PM
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Remove the cover from the motor unit and look at the drive gear. It may be going bad and causing your problem. It is white nylon and is just in front of the motor. If it's causing your problem it will be obvious.

    Bookmark   January 14, 2009 at 6:36PM
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Okay, so I replaced the sprocket, that solved the jerking problem, now it is smooth when it opens and closes. However, it will not open all of the way (stops about 1 foot before it reaches the top) and when it closes, it tries to close too much and the bar gets bent up like it's going to snap and the door reverses and goes back up (but not all the way). I've adjusted the up and down limits and the force. I was able to get it to go up more by doing this (it originally only went up about 5 feet), but the down problem remains the same.

When I manually open to waist height, it falls back down. Am I correct in thinking this is a spring problem and need to call a pro? Or is there something else I can try first?

    Bookmark   January 21, 2009 at 7:04AM
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You have a couple problems at this point. You are right in that you have a spring problem and this is likely what caused your gear to give out. The other problem is the chain was reinstalled at the wrong point. I would call a pro and be sure to tell him that you changed the gear and have adjusted the limits. Shouldn't take him long.

    Bookmark   January 21, 2009 at 9:49AM
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Thanks again for the post don, I've determined it's not a spring problem, the door actually stays in place at waist and shoulder height when opening manually, I called the co. that installed the door and they said that's normal. It's gotta be that the chain was not reinstalled at the correct point as you suggested. When I reinstalled the chain, the part where you screw the chain to the trolly was all the way towards the door, do you know where exactly it should be? Or where I should have my chain setting on the bar when I screw it in again?

    Bookmark   January 21, 2009 at 2:42PM
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Here is the easiest way to get the chain in the right spot. Loosen and remove the chain from the sprocket above the motor. Run the motor until that sprocket runs counterclockwise and stops. With the door in the open position replace the chain. Don't over tighten. You will now have to readjust the up and down limits. If the chain is too tight or loose you will hear it click as it moves. This is bad.

    Bookmark   January 21, 2009 at 3:11PM
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I'll try this today, I had the door closed when I replaced the chain before, and I didn't run the motor without the chain, so maybe that was my problem. Since I'll have it open now, where on the bar does the trolley need to be? When the door was closed, I had it all they way at the end (opposite end from motor), will I have it towards the motor this time since the door will be up and in the way?

    Bookmark   January 25, 2009 at 7:49AM
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Leave everything hooked up except the chain. If you do this the trolley will be where it should be.

    Bookmark   January 25, 2009 at 2:03PM
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