Garage Door Opener Not Working: Which Part Is It?

Openers fail in patterns. Find your symptom below and you’ll usually know which part it is, and roughly what it costs, before you pick up the phone.

”It hums, but the door doesn’t move”

The classic. Inside most chain- and belt-drive openers is a main drive gear made of nylon, and after enough winters it strips its teeth, especially if it has spent those winters pulling a door whose springs are tired. The motor spins but the gear doesn’t bite, so the door sits.

To confirm it, pull the red release cord and lift the door by hand. If the door lifts easily by hand but the opener only hums, it’s the gear. Gear-and-sprocket kits are a standard truck part and this is a routine repair, far cheaper than a new opener.

One warning: if the door is also heavy by hand, the humming opener is the symptom, not the disease. A broken spring kills opener gears by making them drag dead weight.

”The trolley moves, the door stays down”

Look up at the rail. If the little carriage slides back and forth but the door doesn’t come along, the trolley is disconnected. Either someone pulled the red cord (it happens during power outages and never gets re-engaged) or the trolley’s clip broke.

Re-engaging is free. On most units, pull the cord toward the door and run the opener, and the trolley clicks back in as it passes. If it won’t hold, the trolley needs replacing, which is a modest part.

”It starts to close, then reverses”

Two suspects, in order:

1. Safety sensors. Check both LEDs near the floor. Blinking or dark means blocked, dirty, fogged, or knocked out of alignment. A snowbank shovel-lean is the usual culprit in this county. Square them up and wipe the lenses.
2. Force and travel limits. If the sensors are solid but the door touches down and pops back up, the closing-force or down-limit setting has drifted, or the door is binding in cold weather and the opener reads the resistance as an obstruction. This one’s an adjustment, and worth doing right. Set the force too high and the door stops reversing when it should, and that’s a safety system you actually want working.

”The remote barely works anymore”

Range that shrank from the driveway to three feet is usually the remote battery, then the opener’s antenna wire (make sure it hangs down, not tucked up), then interference. LED bulbs in the opener’s own light sockets are notorious for it. Swap in a name-brand LED rated for garage door openers, or an incandescent, and range often comes right back.

”It’s dead. Nothing. No lights.”

Check the outlet first, since a tripped GFCI is the usual cause and the reset button fixes it. After that, suspect the logic board. On a unit under ten years old a board is worth replacing. On the 20-year-old unit that came with the house, put the money toward a new opener with battery backup. The repair-or-replace math is honest, and sometimes replacement genuinely wins.

The five-minute rule

If you’ve spent five minutes and the symptom doesn’t match anything here, stop, especially if there’s grinding, banging, or a door that moves crooked. Describe what you’re seeing and hearing and you’ll get the likely part named on the phone, with the price in writing from our published table before anyone rolls a truck.