LiftMaster 3255 3255 Manual - Page 30

Bell Wire Diagnostics Located On Motor Unit Safety Reversing Sensor LED or Diagnostic LED "Learn" Button Diagnostic Chart Installed Safety Reversing 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. 1 FLASH Safety Reversing Sensors wire open (broken or disconnected). OR 2 FLASHES Safety Reversing Sensors wire shorted or black/white wire reversed. 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. 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. 30