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sears garage door opener - safety mechanism failure

Posted by walton (My Page) on
Thu, Jun 14, 07 at 14:11

Hi out there!
I've just finished changing the worm and drive gears on a 1995 Sears chain-drive GDO. The chain linkage and the arm that connects the chain to the door had been disconnected before I arrived. I THINK I put everything together properly (I'm a pretty handy fixitman) and figured out the Limits and Force adjustments but the safety-reverse on the door doesn't work properly. It only reverses several seconds after encountering massive resistance.

In addition, while repeatedly testing the unit the capacitory began sizzling and leaking oil! I found that the motor was also quite hot.

Anybody have ideas as to the motor/capacitor problem and as to how to make the safety reverse feature more sensitive?

Thanks,
Walton


Follow-Up Postings:

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RE: sears garage door opener - safety mechanism failure

Decrease the down force. This control should be set just high enough for the door to close consistently. It does affect the safety of the unit but there will always be some hesitation before the door reverses. Replace that start capacitor.


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RE: sears garage door opener - safety mechanism failure

Thanks very much Don and sorry for not responding earlier - the computer was down for a while.

The down-force seems to be adjusted to the bare minimum, yet the reverse still doesn't kick in until a dangerously crushing force is exerted. Any other possibilities in sight? Can the leaky capacitor be at fault here?

Thanks again!


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RE: sears garage door opener - safety mechanism failure

The leaky capacitor will not affect the safety but I would replace it before your opener quits altogether. It is normal for there to be a delay before the door reverses when it encounters an obstruction. This feature is controlled by the RPM sensor. When everything is working the RPM sensor board sends a pulse to the logic board. When the door hits an obstruction and the motor stalls, the pulse is no longer there and the logic board reverses the door to the open position. The delay is the time between hitting the obstruction and the motor actually stalling. Hope this helps you to understand the operation.


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RE: sears garage door opener - safety mechanism failure

Very interesting. Can you think of anything that might be delaying the actual stall? Possibly a poor adjustment of the chain tension?
I don't know where the RPM sensor is but I think I remember some kind of sensor or LED covered by a perforated plastic spinner over the motor axle on the side opposite the worm gear. Is that a possible trouble spot? Could the perforated cap be in the wrong position?
Thanks again, etc. etc.


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RE: sears garage door opener - safety mechanism failure

None of those are trouble spots for the problem you are describing. Put a 2x4 on the ground in the center of the door, close the door the door should hit it and after a couple of seconds reverse. If you see your opener rail bowing up and hear wood splitting before reversing, then I would consider that dangerously crushing force and if the forces are turned all the way down your circuit board has gone bad on you otherwise it is working correctly.

*Even with the forces turned all the way down it is still going to exert some force before reversing*


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