Diagnostic Chart - Chamberlain POWER DRIVE 7920KD Assembly & Installation Manual

DIAGNOSTIC CHART

Bell Wire
Safety Reversing Sensor
1 FLASH
Safety reversing
sensors wire shorted
or black/white wire
reversed.
OR
2 FLASHES
Safety reversing
sensors wire open
(broken or
disconnected).
3 FLASHES
Door control or
wire shorted.
4 FLASHES
Safety Reversing
Sensors slightly
misaligned (dim or
flashing LED).
5 FLASHES
Motor overheated
or possible RPM
sensor failure.
Unplug to reset.
6 FLASHES
Motor Circuit Failure.
Replace Receiver
Logic Board.
Diagnostics
Located On
Motor Unit
KG KG
LED or
Diagnostic
LED
"Learn"
Button
Symptom: One or both of the Indicator lights on the safety sensors do
not glow steady.
• Inspect sensor wires for a short (staple in wire), correct wiring polarity
(black/white wires reversed), broken or disconnected wires, replace/attach
as needed.
• Disconnect all wires from back of motor unit.
• Remove sensors from brackets and shorten sensor wires to 1-2 ft
(30-60 cm) from back each of sensor.
• Reattach sending eye to motor unit using shortened wires. If sending eye
indicator light glows steadily, attach the receiving eye.
• Align sensors, if the indicator lights glow replace the wires for the sensors. If
the sensor indicator lights do not light, replace the safety sensors.
Symptom: LED is not lit on door control.
• Inspect door control/wires for a short (staple in wire), replace as needed.
• Disconnect wires at door control, touch wires together. If motor unit
activates, replace door control.
• If motor unit does not activate, disconnect door control wires from motor
unit. Momentarily short across red and white terminals with jumper wire. If
motor unit activates, replace door control wires.
• If motor unit doesn't operate, motor unit is overheated. Wait 15 minutes and
retry. If motor unit still will not operate replace logic board.
Symptom: Sending indicator light glows steadily, receiving indicator light
is dim or flashing.
• Realign receiving eye sensor, clean lens and secure brackets.
• Verify door track is firmly secured to wall and does not move.
Symptom: Motor has overheated; the motor unit does not operate or
trolley is stuck on stop bolt = Motor unit hums briefly; RPM Sensor =
Short travel 6-8" (15-20 cm).
• Unplug unit to reset. Try to operate motor unit, check diagnostic code.
• If it is still flashing 5 times and motor unit moves 6-8" (15-20 cm), replace
RPM sensor.
Symptom: Motor unit doesn't operate.
• Replace logic board because motor rarely fails.
Your garage door opener is programmed with
self-diagnostic capabilities. The "Learn" button/diagnostic
LED will flash a number of times then pause signifying it
has found a potential issue. Consult the Diagnostic
Chart below.
Installed Safety
Reversing Sensor
26