Chamberlain WHISPER DRIVE HD900D - Manual (Page 29)

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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.
• Too much force on garage door will interfere with proper
operation of safety reversal system.
• NEVER use adjustments to compensate for a binding or
sticking garage door.
• After ANY adjustments are made, the safety reversal system
MUST be tested. Door MUST reverse on contact with 1-1/2"
(3.8 cm) high object (or 2x4 laid flat) on floor.
ADJUSTMENT STEP 2
Set the Force
The force setting measures the amount of force required to
open and close the door.
1. Push the purple button twice to enter into the Force
Adjustment Mode. The LED will flash quickly.
2. Push the door control or programmed remote control. The
door will close (DOWN).
3. Push the door control or programmed remote control again.
The door will open (UP).
4. Push the door control or programmed remote control a third
time to close the door (DOWN).
The LED will stop flashing when the force has been programmed.
The door must travel through a complete cycle, up and down, in
order for the force to be set properly. If the garage door opener
cannot open and close the door fully, inspect the door to ensure
that it is balanced properly and is not sticking or binding.
If the door is not stopping exactly where you would like it, repeat
Program the Travel Limits.
Black Button
Purple Button
LED
Push Purple button
twice to enter
unit into Force
Adjustment Mode
Figure 2
OR
Figure 3
Figure 1
Purple Button
Black Button
LED