I think your problem is with your old door. You said it is an old wooden
door. I bet it weighs a ton and is a real strain on your opener. The newer
doors are much lighter in weight. I would replace the door if it were me.
Those who complain about Sears openers I believe are wrong. They are
Chamberlain openers and are not made by Sears. Chamberlain sells the most
openers in the industry and have numerous brand names put on them. I think
they even make them for Stanley.

"despondent" wrote in message
...
Within the past week or so, since the weather turned colder (20F as a
high), the door begins to close and then reverses itself. This
happens at various points, so I do not believe it to be something
directly in the track itself. There does not appear to be anything
inside the garage that is tripping the sensor (i.e., at first we
thought the car bumper was in the way or something like that), however
when viewing the door close from the outside, it looks like maybe the
wood is bulging at a seam and is squeezed just enough to trip the
opener.

Search for the recent thread (started by me) titled "Another Craftsman
Garage OPener Start/Stop Problem with Partial Solution".

In my case, when I disconnected the door, the opener still stopped and
started. This ruled out a door resistance problem. Throwing the
up/down forces to high or max made the door work again but didn't fix
the root cause. Lubing the chain with white lithium grease spray and
spraying the gear assembly with same solved the problem... door goes
up and down fine at low force.

The spray can be had from Home Depot for three bucks or so... do a
search at homedepot.com for it.