Chamberlain Liftmaster Security+ 3900PLD Owner's Manual page 16

MOUNTING AND WIRING THE SAFETY REVERSING
SENSORS
• Slide a 1/4"-20x1/2" carriage bolt head into the slot on
each sensor. Use wing nuts to fasten safety reversing
sensors to brackets, with lenses pointing toward each
other across the door. Be sure the lens is not obstructed
by a bracket extension (Figure 5).
• Finger tighten the wing nuts.
• Run the wires from both safety reversing sensors to the
operator. Use insulated staples to secure wire to wall
and ceiling.
• Strip 7/16" (11 mm) of insulation from each set of wires.
Separate white and white/black wires sufficiently to
connect to the operator quick-connect terminals: white to
white and white/black to grey (Figure 6).
ALIGNING THE SAFETY REVERSING SENSORS
• Plug in the operator. The indicator lights in both the
sending and receiving eyes will glow steadily if wiring
connections and alignment are correct.
The sending eye amber indicator light will glow regardless
of alignment or obstruction. If the green indicator light in
the receiving eye is off, dim, or flickering (and the invisible
light beam path is not obstructed), alignment is required.
• Loosen the sending eye wing nut and readjust, aiming
directly at the receiving eye. Lock in place.
• Loosen the receiving eye wing nut and adjust the safety
reversing sensor until it receives the sender's beam.
When the green indicator light glows steadily, tighten the
wing nut.
Figure 6
WHT/RED
WHT
To Door Control
To insert or release wires, push
in tab with screwdriver tip.
To CableT ension Monitor
Connect Wire to
Quick-Connect
Te rminals
Sensor
Connections
WHT/BLK
WHT
Quick-Connect Terminals
Figure 5
Carriage Bolt
1/4"-20x1/2"
TROUBLESHOOTING THE SAFETY REVERSING
SENSORS
1. If the sending eye indicator light does not glow steadily
after installation, check for:
• Electric power to the operator.
• A short in the white or white/black wires. These can
occur at staples, or at operator connections.
• Incorrect wiring between safety reversing sensors and
operator.
• A broken wire.
2. If the sending eye indicator light glows steadily but the
receiving eye indicator light doesn't:
• Check alignment.
• Check for an open wire to the receiving eye.
3. If the receiving eye indicator light is dim, realign
either sensor.
NOTE: When the invisible beam path is obstructed or
misaligned while the door is closing, the door will reverse.
If the door is already open, it will not close.
Bell Wire
Motor unit
S ensor
Safety Reversing Sensor
16
Safety Reversing Sensor
Sensor
Invisible Light Beam
Protection Area
Wing Nut
1/4"-20
Lens
Bell Wire