Garage Door Opener Only Goes 1' then Reverses After Repair


Old 01-28-18, 03:33 PM
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Garage Door Opener Only Goes 1' then Reverses After Repair

Good Afternoon, All -

Starting a couple of weeks ago, whenever the garage door opener was activated; you could hear it but nothing would happen to the door. After looking into it, I found that the gear shaft cleanly broke right below the top sprocket that moves the chain. I ordered this replacement one from Amazon and have invested most of the day into it.

I successfully disassembled the unit, replaced the part, and reassembled everything; but it's not working correctly. Whenever I press the button to activate the opener, it moves the door about 1 foot then reverses in a matter of a couple of seconds. I verified that everything was correctly reassembled and compared pictures I took prior to working on it and don't see anything out of place. Below is the mode I have as well as what else I've tried after searching online:

Chamberlain (Residential)
Model: 7520D
1/2HP 120V / 6Amp
Mfg Date: 06/13/05

Troubleshooting Attempted
- Verified the safety sensors are working and beam not broken
- Verified that garage door moves up & down easily
- Removed chain, moved door from closed to open position, reattached chain and tried again
- Verified that the carriage assembly is adjusted correctly, not obstructed, and moves with the opener
- Adjusted open / close force testing max and min levels (no difference)
- Verified wire connections for sensors was secure & tried reversing them

If you have any suggestions, it would be a huge help. Thank You!!
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Old 01-29-18, 03:24 AM
Doorman2722's Avatar
Join Date: Oct 2005
Location: upstate NY
Posts: 876
Received 12 Votes on 12 Posts
Did you replace the worm gear also? it sounds like an RPM sensor issue. make sure the black interrupter cup got re installed on the end of the motor shaft

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