Garage Door Won't Close - Diagnostic Tree

Symptom

Customer reports the garage door opener will OPEN the door but won't CLOSE it. Door starts to close, then reverses back to fully open. The opener's safety system is doing its job (preventing close on an obstruction) - the diagnostic is "what is it seeing as an obstruction?"

Likely Causes

In order of frequency:

• Photo eyes misaligned or dirty - 50 % of "won't close" calls
• Obstruction in the eye beam (vehicle, bicycle, leaf litter) - 15 %
• Photo eye wiring damaged (cut, crushed, or unplugged) - 10 %
• Close-force setting too low - 8 %
• Failed opener logic board - 7 %
• Misadjusted down-limit (opener thinks it hit the floor early) - 5 %
• Door binding mechanically - 5 %

Diagnostic Steps

1. Look for blinking lights on the opener. Most brands flash an error code when the photo eyes don't see each other (e.g. LiftMaster blinks the work light, Genie blinks an LED on the motor head). Decode the blink count against the manufacturer chart.
2. Inspect the photo eye LEDs. Both eyes should have a steady LED when aligned. If one is dark or blinking:

• Wipe lenses clean of dust and cobwebs
• Adjust mounting bracket to point eyes directly at each other
• Verify both are 6" or less above the floor on the same plane

1. Test by holding the wall button. Most openers will close on a held-button push regardless of photo eyes (the safety override). If it closes this way, you've confirmed the eyes are the problem. Don't leave it "fixed" by overriding - replace or repair the eyes.
2. Check the photo eye wiring. Trace from eyes back to the opener. Look for cuts, staples through the wire, mouse damage, or wires not seated in the terminal block.
3. Test the close force. With the opener in close mode and you pushing UP on the door, the door should resist with enough force to overcome a 25 - 30 lb upward push but not significantly more. Too low = won't fight a slight resistance = reverses. Adjust per opener manual.
4. Run the door manually. Disconnect the opener via the emergency release. Push the door up and down by hand. It should glide with ~10 lb effort; if it binds at any point, that's the issue, not the opener.
5. Check the down-limit setting. Open and close cycle while watching where the opener stops. If it stops short of floor and reverses, the down-limit is mis-set.

Resolution

• Eye obstruction: clear the path, brief the customer on keeping the area clear.
• Close force too low: adjust per the opener manual.
• Failed logic board: replace the board OR offer an opener replacement if the unit is > 10 years old (often the better economic choice).
• Down-limit mis-set: adjust per the opener manual.
• Door binding: separate repair - usually rollers, hinges, or track alignment. Quote the repair.

Prevention

• Annual service catches photo-eye drift before it becomes a customer callback
• Customer education: routine alignment with a "wave your hand to test" habit prevents surprises

References

• UL 325 (Door, Drapery, Gate, Louver, and Window Operators)
• Opener manufacturer service literature
• Manuall internal: Annual Garage Door Service