GDO Craftsman buzzing sound door won't open or close

17 years ago

I have Craftsman 1/2HP 139.18850 (1995).

The door or remotes won't open the door and I found another post that seems the same problem. "When pressing the wall button or outside keypad the motor (41A4315-7C) hums twice and does nothing. The green light up on the motor blinks 5 times, stops, blinks 5 times and so on"

Seems to indicate...The LED is blinking the code for "RPM sensor or motor overload".

I bought the 41C4398A RPM sensor assembly part and replaced it and the same problem happens so it's not the sensor itself.

My gears (worm, drive) look fine to me, a little chewed but still look 100% fine to me.

What else could cause the RPM sensor to stop the motor from turning? Is there some way to force turn the mechanism to see if it's jammed on a gear or tooth.

Not sure what to try next.

Andrew

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Comments (2)

don_1_2006
17 years ago
The RPM sensor will not stop the motor from running. There is a possibility the start capacitor is bad if your door is closed and will not open. If the door is open and will not close it could be the trolley is jammed against the bolt just in front of the motor housing. What was your original symptom?
newday3000
Original Author
17 years ago
Thanks for the info. I used a couple of posts here to figure it out and fix it. I fixed it just now using this information.

Is the trolley (the thing the door is connected to) jammed against the bolt just in front of the motor unit? If so you can remove that bolt and then run the opener until the door is closed. While it is closed adjust the 'up limit' a couple turns in the opposite direction of the arrow printed on the cover? That control is on the side of the unit. Be sure to replace the bolt.

Andrew
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