Garage Door Opener Help

[Bob Coleman]

Having a bit of trouble with my garage door opener and am hoping someone here can help!

I have a chain drive liftmaster, made in 1999 and I couldn't find a model number that matches current numbers. It looks very close to model 1355.

The chain had been sagging for a while, but I figured I would just replace the worn out bearings, etc when everything finally broke. Well, last weekend it broke. The shaft sheered just below the sprocket, so I ordered a replacement kit, and put everything back together this afternoon.

However, when I tried it, the trolley runs a little ways in the down direction, then reverses and runs a foot or so in the up direction and stops. It does this independent of the position of the up or down limits (it will stop if it hits one, but if I move the limits all the way to the extremes, it stops as I described without touching the contacts)

I tried adjusting the up and down force with no change in symptoms.

Does anyone have an idea what might be wrong? I already shelled out for the repair parts, I'd rather not have to buy a new unit!

Is it possible I screwed up the wiring?

Thanks in advance!

[Bill Huber]

This is with the door not connected to the chain or is it pulling the door with it when this happens.

Could you have a problem with the door beam stops if you have them.

[Jerome Stanek]

Have you tried unplugging and plugging it back in? I had a sears that did that and unplugging it reset the control board.

[Lee Schierer]

There's likely a third adjustment that is set improperly. Most door openers have a raise/lower force limiter to prevent the door from crushing something when it closes. It sounds like you need to increase the torque on the chain drive sprocket. Look for a nut with a spring below it on the main sprocket drive shaft and tighten it about 1/2 turn at a time until the opener moves the full length of travel allowed by your up and down stops. You may need to increase this once you connect the door.

[Bill ThompsonNM]

Or, if it has a photocell and light beam to detect an object -- they are misaligned or the connecting wires have been disrupted.

[Larry Browning]

There's likely a third adjustment that is not set improperly.
Well then he needs to leave it alone if it is not set improperly!
I read this, and just couldn't resist. Sorry! I tried to resist, really I did!

[Bob Coleman]

Ok, I figured it out. Root cause was owner idiocy. 2 issues:

1: The door travel traveler was at the wrong end - not sure how that happened.

2: I forgot to replace the RPM limiter cap on the motor shaft, so after a certain amount of time, the motor stopped.

Thanks for the help!