Garage door won't reverse when hitting an object

11 years ago

I have an old Craftsman garage door opener, model 139.53535SRT1 with logic board 41A4315-6C. If I adjust the down force to the minimum, the door will travel about a foot and then reopen, as expected. If I increase the force just slightly -- even to 1.5 out of 9 -- the door will close but will not reverse on a 2 x 4 on the floor or if I hold the door with my hand when it is closing.

I'm considering replacing the logic board, but someone suggested that the RPM sensor is at fault or is just blocked by dirt. If the RPM could not be detected correctly, would that cause the door to fail to reverse, or would it make it fail to close?

Could some other simple problem, such as bad contacts or a loose wire, cause the door not to reverse on an object? It does reverse properly if something interrupts the beam of the safety sensors.

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Comments (4)

randy427
11 years ago
Two things come to mind:

Is the chain properly tensioned? Does encountering the obstruction cause the steel bean to visibly deflect? If the chain is too loose, the obstruction sensors in the drive unit may not react before it 'thinks' the door is fully closed. (does a 6" obstruction cause it to reopen?)

also, When the neoprene gears in the motor unit start to wear, they create plastic debris that could be defeating one or more of the internal mechanical switches. (not as likely, but still possible)
bhucker
Original Author
11 years ago
I think we can rule out the chain. It was sagging, and I tightened it -- not because I suspected that it caused this non-reversal problem but just to get it back to normal.

Would plastic debris affect the RPM sensor? If so, could that explain this problem?
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randy427
11 years ago
I don't see how the RPM sensor would be a factor here, but it's only a few screws to open the case and see if there's a bunch of white grindings in it.
bhucker
Original Author
11 years ago
OK, thanks. This is a rental, so it's not quite as simple as walking out to my garage. I need to notify the tenant, pack some tools and drive there.