Chamberlain LiftMaster PROFESSIONAL SECURITY+ 3255-2CM Manuel Du Propriétaire page 23

ADJUSTMENT STEP 1
Adjust the UP and DOWN Travel Limits
Limit adjustment settings regulate the points at which the
door will stop when moving up or down.
To operate the opener, press the Door Control push bar.
Run the opener through a complete travel cycle.
• Does the door open and close completely?
• Does the door stay closed and not reverse
unintentionally when fully closed?
If your door passes both of these tests, no limit
adjustments are necessary unless the reversing test fails
(Adjustment Step 3, page 25).
Adjustment procedures are outlined below. Read the
procedures carefully before proceeding to Adjustment Step
2. Use a screwdriver to make limit adjustments. Run the
opener through a complete travel cycle after each
adjustment.
NOTE: Repeated operation of the opener during
adjustment procedures may cause the motor to overheat
and shut off. Simply wait 15 minutes and try again. If
anything interferes with the door's upward travel, it will
stop. If anything interferes with the door's downward travel
(including binding or unbalanced doors), it will reverse.
HOW AND WHEN TO ADJUST THE LIMITS
• If the door does not open completely but opens at
least five feet (1.5 m):
Increase up travel. Turn the UP limit adjustment screw
clockwise. One turn equals 2" (5 cm) of travel.
NOTE: To prevent the trolley from hitting the cover
protection bolt, keep a minimum distance of 2-4"
(5 cm - 10 cm) between the trolley and the bolt.
• If door does not open at least 5 feet (1.5 m):
Adjust the UP (open) force as explained in Adjustment
Step 2.
• If the door does not close completely:
Increase down travel. Turn the down limit adjustment
screw counterclockwise. One turn equals 2" (5 cm) of
travel.
If door still won't close completely and the trolley bumps
into the pulley bracket (page 4), try lengthening the door
arm (page 21) and decreasing the down limit.
• If the opener reverses in fully closed position:
Decrease down travel. Turn the down limit adjustment
screw clockwise. One turn equals 2" (5 cm) of travel.
Without a properly installed safety reversal system, persons
(particularly small children) could be SERIOUSLY INJURED or
KILLED by a closing garage door.
• Incorrect adjustment of garage door travel limits will
interfere with proper operation of safety reversal system.
• If one control (force or travel limits) is adjusted, the other
control may also need adjustment.
• After ANY adjustments are made, the safety reversal system
MUST be tested. Door MUST reverse on contact with 1-1/2"
high (3.8 cm) object (or 2x4 laid flat) on floor.
To prevent damage to vehicles, be sure fully open door
provides adequate clearance.
Cover Protection
Bolt
2-4"
(5-10 cm)
• If the door reverses when closing and there is no
visible interference to travel cycle:
If the opener lights are flashing, the Safety Reversing
Sensors are either not installed, misaligned, or
obstructed. See Troubleshooting, page 18.
Test the door for binding: Pull the emergency release
handle. Manually open and close the door. If the door is
binding or unbalanced, call for a trained door systems
technician. If the door is balanced and not binding,
adjust the DOWN (close) force. See Adjustment Step 2.
23
Left Side Panel Limit Adjustment Screws
Adjustment Label