[Doublej]

My garage door open has decided that instead of closing fully all of the time, sometimes it would rather close almost all of the way and then reopen. This doesn't happen all of the time but the frequency of the problem appears to correlate with increasing temperature.

It's a 10+ year old Liftmaster chain drive. I can't find any pinch points, bad rollers or broken springs. I cranked up the power for the closing force to near full and am stilling having problems. Sensors seem to be fine as well.

Am I missing something here?

At this point I am thinking maybe I just bit the bullet and replace the unit myself and hope the problem goes away.

[mresseguie]

It's important to use lithium grease on the chain up to twice a year. I've experienced the problem you describe, and the garage repair shop guy told me to use this grease.

Give it a shot. It's a helluva lot cheaper than replacing the drive unit and chain.

[Peter J]

Do you have owner's manual?

It's possible you went wrong direction on adjustment. Typically you have force adjustment and closed position adjustment. It sounds like closed adjustment might be off. It meets floor and tries to drive beyond that point, which sensors interpret as an obstruction and since you don't want to squash the cat, it reverses.

Might also be something hanging on door somehow breaking safety beam at bottom of travel, or beam thingies might be loose?

[Peter J]

This might be helpful.

http://chamberlain.custhelp.com/app/answers/detail/a_id/246/~/how-do-i-adjust-the-travel-and-force-limits%3F

Along the same lines as Michael mentioned, chain tension is also a maintenance item, but I doubt connected to problem.

And by the way, Chamberlain makes Liftmaster. As I recall, there are only three or four manufacturers of these things, marketed under different names.

[Doublej]

I think Mike nailed it. I forgot that the bottom part of the rail needs to be lubricated regularly. I siliconed it up and all is functioning well. I was able to dial down the needed torque by 50%.

THANKS!