Your garage door opener is programmed with self-diagnostic capabilities which enable you to identify your potential problem by counting the number of flashes. The instructions below will help you troubleshoot LiftMaster, Chamberlain, and Sears A/C model openers. These three brands make up 70% of the openers that are sold in the United States and are all diagnosed the same way. Here’s what to look for:

  • One flash indicates that your safety sensor wire may be open, broken or disconnected.
  • Two flashes indicate that your sensor wire is either shorted or the black and white wires could be reversed. In both cases, your safety eyes will not glow steadily. You should inspect the wiring for any staples or incorrect wiring. To test if your wires are shorted, you must detach the wires and reattach the sending eye and receiving eye separately to the opener to see which wire does not light. If the sensors are aligned and the lights glow, then the wires need replacement. If the lights do not glow, then the safety sensors need to be replaced.
  • Three flashes are connected with the door control or wire being shorted. Check the door control wires for staples in it just as you did for the safety sensors wires. You can also disconnect the door control wires and touch them together.
  • Four flashes are usually the most common reason your opener lights may be flashing, because of your sensor eyes being misaligned. If an object has misaligned your sensor eyes then it breaks the electronic beam preventing the garage door to close properly. The door will stop and reverse back upwards.
  • Five flashes indicate that your motor may be overheated or there may be a RPM (revolutions per minute) sensor failure. Unplug your unit to reset it. If it continues to flash, then your RPM sensor must be replaced. If the motor unit still does not operate at all, then it has overheated and the logic board must be replaced.
  • Six flashes designate a motor circuit failure. The motor unit completely does not work so the receiver logic board must be replaced.

Still having trouble? Contact a professionally trained garage door technician who can help diagnose the problem.

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