Chamberlain 248739 - Manual (Page 28)

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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 fl at) on fl oor.
To prevent damage to vehicles, be sure fully open door
provides adequate clearance.
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 30).
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 fi ve 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 26) 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.
• If the door reverses when closing and there is no
visible interference to travel cycle:
If the opener lights are fl ashing, the Safety Reversing
Sensors are either not installed, misaligned, or
obstructed. See Troubleshooting, page 23.
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.
Cover Protection Bolt
2-4"
(5 cm-
10 cm)
Left Panel Limit Adjustment Screws
ADJUSTMENT LABEL