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Bearcat Company - Liftmaster Trouble Shooting

LiftMaster Chamberlain Craftsman

Garage Door Opener Trouble Shooting

Trouble Shooting Liftmaster Openers

Bearcat Company has provided some basic trouble shooting for LiftMaster, Chamberlain and Craftsman garage door openers. Chamberlain Group manufactures Liftmaster Professional, Chamberlain and Craftsman making them similar in many respects. Following a process of systematic elimination may help trouble shoot your garage door opener, before calling the manufacture or a local garage door repair service company. Remember Safety First.

  General Troubleshooting

The most important step in servicing the garage door opener is the isolation of the faulty section.
The technician must decide if the problem is in the:
  • Installation
  • Opener Mechanism
  • Remote Control
  • Radio Receiver/Logic Circuit


The opener should be installed in such a manner as to provide smooth operation.
  • Any "jumping" of the door and hardware on initial movement, could mean that the opener mechanism is pushing or pulling at the wrong angle -- check the installation.
  • Disconnect the trolley by pulling the manual release of the opener and move the door by hand to ensure that the door is balanced. A weak spring could mean that the opener is required to to lift the weight of the door. The opener may be capable of doing this, but a most important feature will be lost -- SAFETY. Any major door repairs should be completed prior to the installation.

Opener Mechanism

Disconnect all control wires, but not the sensor wires, at the rear or side of the opener and momentarily short the red and white terminals together (with a small jumper wire). The opener should operate if no problem exists. If the opener does not function use the troubleshooting chart.

Solid State Microprocessor Logic Board

Receiver/Logic boards manufactured with "Yellow" or "Blue" Force Adjustment dials incorporate self-diagnosing capabilities. A diagnostic "flashing LED" found next to the "learn button" can be used to troubleshoot some problems with the opener. The chart below will assist in isolating the most common electrical difficulties.

# of flashes







Rapid Flashing


  The Protector System wire open or totally misaligned

  The Protector System wire shorted or black/white wire reversal

  Door Control or Multi-Function control Panel wire shorted

  IR sensor slightly misaligned (dim or flashing sensor LED)

  Motor overheated/Possible RPM sensor failure -- unplug to reset

  Motor circuit failure -- replace RX/LX board

  Liftmaster transmitter with the correct format code being received
  (opener not necessarily programmed to respond)

  Troubleshooting Symptom Diagnosis

Warning: Always disconnect power to garage door opener before removing or installing outside cover !

1. Garage door opener does not operate from door control push button or remote control:     
  • No power. Check to make sure the outlet has power. Plug in the opener. There may be a light switch that turns the outlet "On" make sure that it is on. Also check fuse box or circuit breaker.
  • Overload protector tripped in motor. wait 15 minutes, after the motor has cooled down try to operate again.
  • Shorted door control or shorted bell wire. Remove wires and retest. Repair bell wire or door control

2. Door operates from door control push button, but not from the remote control:     
  • Remote control battery may be dead. Change battery and try again.
  • Remote control may not be sending a signal. If more than one remote, check that both are working.
  • Lock switch is ON. Check for a blinking light on the Multi-Function Control Panel. If so push lock button to turn OFF.
  • Code remote control to receiver.

3. Garage door opener operates from door remote control, but not door control push button:     
  • Door control may be defective. Disconnect wires from door control, short white and white/red wires to see if the unit operates. If the unit works replace the door control.
  • Open bell wire. Disconnect wires from the receiver logic board, short white and red terminals to see if the unit operates. If the unit works replace/repair the bell wire.

4. Remote control has short range:     
  • Weak battery. Replace battery and try again. If two remotes are available, try both for comparison.
  • Remote to close from inside roof of car. Pull the visor down and retest. If the unit operates, the visor will have to remain down when using the remote.
  • Metal door or siding. Open garage door if the range increases, Antenna Extension Kit 41A3504 may be required.
  • RF interference may be causing the problem. Locate interference, disable if possible.
  • Possible defective receiver/logic board. ( rare on newer units )

5. Garage door opener does not shut of at the end of travel:     
  • Check limit travel adjustment first.
  • Limit contacts not operating. Remove cover and manually observe the switch actuator. Check continuity of contacts. Possible bad assembly.
  • Check gear and sprocket assembly for wear. Check shaft for play or wobble. Worn assembly can cause unit to go out of sync.

6. Garage door opens and/or closes by itself:     
  • Stuck remote control button. Check all remotes. check LED on receiver.
  • Staples around Multi-Function Control Panel bell wire could be cutting into that wire. Remove wires from opener and test. Replace staples causing intermittent short.
  • Multi-Function Control Panel could have sticking door control push bar. Remove wires from control panel and test. Replace control panel if defective.

7. Motor hums, will not run:     
  • Trolley jammed into stop bolt. Visually check location of trolley. Repair as necessary and readjust limits.
  • Defective capacitor. Subsitute a known good capacitor. Replace if problem fixed.
  • Defective wiring or connector(s) in capacitor circuit. Check for continuity. Repair wire or connector(s).
  • Defective motor bearings. Remove motor, try to turn shaft by hand. If the shaft will not turn freely, replace the motor.

8. Full force is applied before door will reverse:     
  • Force control out of adjustment. Decrease force by turning control counter clockwise.
  • Defective logic board. Replace and retest.

9. Door closes completely and immediately opens fully:     
  • Down travel improperly adjusted or defective. Adjust the Down limit and retest. If the limit assembly is defective replace.
  • Obstruction causing door to reverse. Pull emergency release. Open and close the door manually while checking for obstruction. Remove obstruction.
  • Defective door hardware causing the door to reverse. Open and close the door manually while checking for defective hardware. May require the service of a garage door professional.
  • Ice or snow buildup under door. Inspect the area around the base of the door and look for any ice or snow buildup. Remove buildup. If limit switch is adjusted to compensate for buildup, door will not close fully when ice or snow has melted.
  • Gear assembly wearing. Remove cover and inspect for wear and plastic shavings. This influences the sync of the door and opener. Replace gear with kit or assembly.

10. Door starts to open/close only travels 8" then reverses/stops:     
  • Forces for up/down set to low. Pull emergency release and check manual door operation. If no obstruction, increase force and retest.
  • Interupter cup not properly seated on motor shaft. Visually inspect the interupter cup to insure proper installation. Repair or replace if necessary.
  • Defective RPM board. Replace and test.
  • Defective logic board. Replace and test.

11. Door does not close, light on garage door opener flashing:     
  • Check The Protector System. Both sensors must be aligned or aimed across the door opening without any beam obstruction. Remove any obstruction or align both sensors.
  • Check for spider webs and/or dirty lenses. Wipe clean.
  • Make sure both LED lights are solid on each sensor housing.
  • Check safety sensor wiring and connections to the power head unit. Repair as necessary.
  • Check for diagnostic flashing code "1". Located at the power head unit.
  • Try replacing safety sensors. Retest.

12. The motor runs but the door does not move:     
  • Check to see if trolley is disengaged into manual mode. Reconnect for automatic operation.
  • Check for a striped gear or drive rack. Replace parts as necessary.

13. Door does not close completely:     
  • The travel limits may need to be adjusted. Pull emergency release and check door travel to ensure that it operates smoothly. If so, adjust travel limits.
  • Door may be obstructed. Remove obstruction.
  • Check limit switch contacts and cams for excessive play or looseness. Replace if necessary.

14. Door does not open completely:     
  • Is something obstructing the door? Is it out of balance, or is there a broken spring? Remove the obstruction. Repair broken spring or balance the door properly.
  • If the garage door is in good working order but still doesn't open all the way, increase the up force.
  • If the garage door openers at least five feet, the open travel limit may need to be increased. One turn equals 2 inches of travel. Repeat the safety reverse test after the adjustment is complete.

15. Light does not go on when door opens:     
  • Light bulb could be out. Inspect light bulb and replace if necessary.
  • Light socket could be damaged. Check for voltage where the light socket leads connect to the terminal board.
  • Defective receiver/logic board. Unplug and plug back in AC cord. Listen for relay click on logic board. If click is heard, check for defective socket or wiring.

16. Light does not go OFF after delay period:     
  • Work light switch "on". Turn off work light switch.
  • Defective Multi-Function Control Panel. Replace with functioning panel.
  • Defective receiver/logic board. Replace defective logic board if necessary.

17. Garage door opener strains or needs maximum force to open and close:     
  • The garage door may be out of balance or a spring may be broken. Close the door and use the emergency release handle to disconnect the trolley. Open and close the door manually. A properly balanced door should stay at any point of travel while being supported entirely by it's spring(s). If it does not, disconnect the garage door opener and call a garage door professional. Do not increase force to operate the garage door opener.