Garage door won't close: watch where it quits, then count the blinks

A door that opens fine but refuses to close has already ruled out the expensive stuff. The spring lifts, the motor runs, the door travels. What’s left is the close-cycle safety logic, and it reports its own faults in two places: where the door gives up, and the blink pattern on the opener light. Read both and you’ve usually got the diagnosis before you’ve touched a tool.

First: where does it quit?

• Won’t start down at all - light flashes, door stays put. The opener is refusing the command. Ninety-something percent of the time that’s the safety sensors: blocked, misaligned, or unplugged. This is the classic “works from the wall button if I hold it down” fault - holding the button bypasses the sensors, tapping it doesn’t.
• Starts down, reverses within a foot or two. Usually still sensors - sunlight glare or a sagging bracket that only breaks the beam once the door starts moving and the frame flexes. Late-day sun down a west-facing Kokomo driveway hits one sensor dead-on; shade that sensor with a cupped hand and test again. A cardboard sleeve is the permanent version of the fix.
• Reverses right at the floor. The door is touching something - or thinks it is. Check for gravel, an extension cord, a garden-hose end under the threshold. If the floor is clean, the travel limit is set a hair long: the door presses the slab, reads it as an obstruction, and retreats. That’s an adjustment, not a part.
• Closes fully, then pops back open. The close-limit and close-force settings need re-balancing against each other. Also an adjustment, not a part.

Second: count the blinks

When an opener refuses to close, the motor-head light doesn’t just flash randomly - it flashes a code. On most units (LiftMaster, Chamberlain, and kin) it’s a repeating count: four blinks means sensors misaligned, five means one sensor isn’t getting power at all. Genie and Overhead Door units blink a colored LED near the learn button instead. Count the pattern, then check the manual’s code table - or just tell us the count when you call. That number turns “it won’t close” into a specific part on a specific wire.

The two-minute sensor fix

Both sensor lights should be on steady - typically one amber (sending) and one green (receiving). A dark or blinking green light means the beam isn’t landing. Loosen the wing nut, swing the sensor gently until the light goes solid, snug it back down. While you’re there, wipe both lenses. A season of mower dust takes out more sensors in Howard County than anything mechanical does.

When it really is the opener

If the sensors show steady lights, the floor is clear, the limits have been set, and the blink code points at the logic board - now you’re in opener repair territory. Boards and receivers are fixable and worth quoting against the age of the unit. And if the door also feels heavy when you lift it by hand with the release cord pulled, stop: that’s not the opener at all, and the close-cycle was just the first symptom. Heavy-door faults live on our main repair page - and they’re the reason we ask you to try the manual lift before we book the visit.

Either way, call with two facts: where the door quits, and what the light blinks. Those two answers usually mean a one-trip fix.