LiftMaster 3950 3950 Manual - Page 18

Motor unit "Learn" Button LED or Diagnostic LED "Learn" Button Diagnostic Chart 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. 9 FLASHES Factory installed jumper loose or missing. Installed Safety Reversing Sensor Your door operator 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. Symptom: One or both of the Indicator lights on the safety reversing 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 feet (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 reversing sensors. Symptom: The door doesn't activate from the 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. Symptom: Door travels 2-3 inches and stops. • Reprogram limits and forces. See Adjustments section. • If the operator continues to travel 2-3 inches, check the travel module connection or replace the travel module. Symptom: Door travels 2-3 inches and stops. • Reengage the emergency release. • Motor may need to be replaced. Symptom: Door reverses while closing. • Check the factory installed jumper at the terminal connections. Factory installed jumper must be in place for proper operation. Operator will not function without the jumper. 18