Chamberlain 2255-2 - Manual (Page 30)

Bell Wire
Safety Sensor
Diagnostics
Located On
Motor Unit
LED or
Diagnostic
LED
"Learn"
Button
30
Installed
Safety Sensor
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 Diagnostic Chart below.
Diagnostic Chart
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.
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 over heated; 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.
• If motor unit doesn’t operate, motor unit is overheated. Wait 30 minutes and
retry. If motor unit still will not operate replace logic board.
Symptom: Motor unit doesn’t operate.
• Replace logic board because motor rarely fails.
Motor Circuit Failure.
Replace Receiver
Logic Board.
Motor overheated or
possible RPM sensor
failure. Unplug to reset.
Safety Sensors
slightly misaligned
(dim or flashing LED).
Door control or
wire shorted.
Safety sensors wire
shorted or black/white
wire reversed.
Safety sensors wire open
(broken or disconnected).
1 FLASH
2 FLASHES
3 FLASHES
4 FLASHES
5 FLASHES
6 FLASHES
OR