There are four separate adjustments that you should do at least once a year on your Chamberlain garage door opener. These include adjustments for the up and down travel limits as well as adjustments for the force necessary to engage the safety mechanisms. You will make all of the adjustments from four different screws that mount to the garage door opener motor head. Adjusting the door opener regularly will help keep it operating at peak performance.
Up And Down Limits
Set up a step ladder under the back of the garage door opener so you can access the adjusting screws on the opener. Have a remote control with you so that you can operate the door as you make adjustments.
Press the button on the remote control to open the garage door. The bottom of the garage door should be just below the header when it opens fully. Also, the opener trolley should be 4 inches from the stop bolt on the back of the rail.
Locate the up and down limit screws on the left side of the opener motor head. Turn the up limit adjustment clockwise to raise the door more or counter-clockwise to lower the door slightly. One full turn of the screw will equal 2 inches of door travel. Operate the door with the remote control to close the door and then reopen the door and check the travel.
Close the garage door using the remote control. The door should seal to the floor. Adjust the down limit screw just as you did the up limit screw. If you adjust too far down the door safety force mechanism will engage causing the door to raise. Continue fine tuning the down limit until the door seals to the floor and does not automatically reverse.
Up And Down Force
Ask a friend to stand outside the door while you operate the door from the remote control. When the door is halfway open have your helper gently grab the bottom section and apply some down force. The door should stop when it encounters an obstruction. If it requires a lot of force to stop the door, adjust the up force limit screw.
Go to the back of the garage door opener and remove the lens cover. The up and down force adjustment screws are on the upper right side of the opener. Turn the up force screw counter-clockwise in small increments. Run the door through a cycle until it is down and then retest as before. Continue making fine-tune adjustments as necessary.
Open the door fully using the remote control. Ask your friend to stand outside the door opening while you operate the door opener with the remote control. Lower the door using the remote control. When the door is half way down have your friend grab the bottom of the door and pull up slightly. The door should stop momentarily and then reverse.
Go to the back of the opener and adjust the down force screw, if the door did not stop immediately and reverse. Turn the adjustment screw counter-clockwise and retest. Run the door to an open position and then retest. Continue making fine-tune adjustments as necessary.