Terrible, are the instructions that came with my Chamberlain LiftMaster Professional garage door opener 1355C, 1/2 hp. Sure, read them, but if you have no clue then try my rough adjustment guideline as a start.
My idler bolt broke, sending my chain flopping down. When I replaced my idler bolt, I had no idea how to get the chain adjusted. Firstly, close your opener. The trolley should be close to your door. put some slack in your chain and then route it through the opener’s gear. Then tighten everything up. Damn there’s nothing about this in the manual. I had to do this by trial and error three times, slackening, getting it into the gears, tightening, repeat 3 times. What a hassle. Clearer instructions would have been a time and frustration saver.
The garage door opener inner trolley is the flat metal object attached to the chain. The outer trolley is the larger box that is attached to the door. Both of mine are silver. When you pull the red handle you disengage the outer and inner trolley, allowing the door to manually open and close.
Inner and outer trolley diagram. Garage door opener
Your trolley should travel between the pulley bracket (fully closed) and the cover protection bolt (fully open). The pulley bracket connects the rail to the wall above the door. If the trolley is hitting the pulley bracket it is traveling too far. Decrease down travel, turn down limit clockwise. The trolley only needs to travel far enough to close the door, which should be a couple of inches in front of the pulley bracket.
Cover protection bolt, between the white light cover of the opener mechanism and the trolley, protects the cover in case the trolley goes too far backward.
On the opposite end is the cover protection bolt. This protects the opener motor if the trolley goes too far back. If the trolley is hitting the cover protection bolt, decrease the up travel turn up limit counter-clockwise. When the door opens it should automatically stop 2-4″ in front of the cover protection bolt. Damn, the 2-4″ is in the manual but does not say how to adjust it. Bad manual.
Now, read the manual. There are 3 common problems:
1. Door does not completely open but opens at least 5′: Increase up travel, turn the up limit adjustment clockwise. If it hits the cover protection bolt, back off on the up travel
2. Door does not close completely: Increase down travel, turn down limit adjustment counterclockwise. 1 turn = 2″
3. Door completely closes, then reverses: Decrease down travel, turn limit adjustment clockwise. 1 turn = 2″
There are 2 other less common problems, read the manual. I’m stuck between case 2 and 3: The door either does not close completely, or it closes completely and reverses. Either way, it does not stop.
