Chamberlain POWER DRIVE PD300 Manual page 30

Adjustments
Step 2 Adjust the Force
Without a properly installed safety reversal system, persons (particularly small children) could be
SERIOUSLY INJURED or KILLED by a closing garage door.
• Too much force on garage door will interfere with proper operation of safety reversal system.
• NEVER increase force beyond minimum amount required to close garage door.
• NEVER use force adjustments to compensate for a binding or sticking garage door.
• 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.
Force adjustment controls are located on the back panel of the motor unit. Force adjustment settings
regulate the amount of power required to open and close the door.
If the forces are set too light, door travel may be interrupted by nuisance reversals in the down direction
and stops in the up direction. Weather conditions can affect the door movement, so occasional
adjustment may be needed.
The maximum force adjustment range is about 3/4 of a complete turn. Do not force controls beyond
that point.
Turn force adjustment controls with a screwdriver.
NOTE: 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 FORCES
1. Test the DOWN (close) force
Grasp the door bottom when the door is about halfway through DOWN (close) travel. The door
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should reverse. Reversal halfway through down travel does not guarantee reversal on a 1-
1/2" (3.8 cm) obstruction. See Adjustment Step 3, page 30. If the door is hard to hold or
doesn't reverse, DECREASE the DOWN (close) force by turning the control
counterclockwise. Make small adjustments until the door reverses normally. After each
adjustment, run the opener through a complete cycle.
If the door reverses during the down (close) cycle and the opener lights aren't flashing,
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INCREASE DOWN (close) force by turning the control clockwise. Make small adjustments until
the door completes a close cycle. After each adjustment, run the opener through a complete
travel cycle. Do not increase the force beyond the minimum amount required to close the door.
2. Test the UP (open) force
Grasp the door bottom when the door is about halfway through UP (open) travel. The door
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should stop. If the door is hard to hold or doesn't stop, DECREASE UP (open) force by
turning the control counterclockwise. Make small adjustments until the door stops easily and
opens fully. After each adjustment, run the opener through a complete travel cycle.
If the door doesn't open at least 5 feet (1.5 m), INCREASE UP (open) force by turning the
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control clockwise. Make small adjustments until door opens completely. Readjust the UP limit if
necessary. After each adjustment, run the opener through a complete travel cycle.
Back Panel
Antenna
29
Force Adjustment Screws
Open Force Close Force