Motor Runs But the Garage Door Stays Put

What causes it

These are the causes we find most often, in roughly the order we check them.

1. 1

   Trolley disengaged from the carriage

   The red release cord uncouples the door arm from the carriage that travels along the rail. It exists so you can move the door in a blackout. Once pulled, the opener happily runs the carriage from one end of the rail to the other while the door hangs exactly where it was left.

   What you can check

   Watch the rail, not the door. If the carriage slides along the rail while the arm bolted to the top panel stays still, the trolley is disengaged. Pull the release cord back towards the door and run one full cycle so it re-latches.

   What we do

   We re-engage the carriage and work out why it came apart. Perished cords, cracked trolley bodies and worn latch pawls all let go on their own, and a trolley that will not hold the latch under load is replaced rather than nursed. We then reset the travel limits and re-test.

2. 2

   Stripped nylon drive gear

   Most sectional openers turn a steel worm against a nylon gear, and the nylon is meant to be the part that gives. Once the teeth shear, the worm spins in a smooth bore. The motor sounds completely normal and the chain never moves a millimetre.

   What you can check

   Look for white or grey plastic swarf on the floor under the opener head, and watch whether the chain or belt moves at all while the motor runs. A motor that sounds healthy with a dead-still chain is the classic signature.

   What we do

   We fit a gear and sprocket kit, pack it with the correct grease and reset the limits. Then we check the door balance, because a gear almost never fails on a door whose springs are still doing their job. Fixing one without the other just books the next call-out.

3. 3

   Chain off the sprocket or a broken belt

   A chain that has stretched past its adjustment can climb the sprocket and drop off the side. A toothed belt can shear its teeth or split at the join. Either way the sprocket keeps turning under the motor with nothing attached to it.

   What you can check

   With the door closed, look along the full length of the rail with a torch. A chain lying slack in the rail channel, a chain hanging below the sprocket, or a belt with an obvious break is visible from the floor.

   What we do

   We refit or replace the chain or belt, set the tension to the manufacturer's figure, and replace a sprocket whose teeth have hooked over. A chain that has come off once on a correctly tensioned rail usually means the sprocket bearing is worn, so we check that too.

4. 4

   Sheared sprocket key or drive coupling

   The sprocket is locked to the output shaft by a small key or grub screw. On a roller door opener the motor couples to the barrel through a driven plate. If that key shears or the grub screw backs out, the shaft turns inside a component that no longer turns with it.

   What you can check

   Listen to the motor and watch the sprocket itself rather than the chain. If the motor runs and the sprocket does not turn at all, the coupling has failed. On a roller door, watch whether the barrel rotates while the motor runs.

   What we do

   We fit a new key, sprocket or coupling plate, re-align the output shaft and lock the fasteners properly. On roller door openers we also check the barrel for a worn keyway, because a chewed keyway will shear a new key within weeks if it is left alone.

5. 5

   Broken door arm or J-arm bracket

   The curved arm bolted between the carriage and the top panel takes the whole push and pull of the door. Its fixing plate is bolted to a single panel, and years of load can crack the bracket, tear the panel skin or shear the clevis pin.

   What you can check

   Look at the top of the door where the arm attaches. A bent arm, a missing clevis pin, elongated bolt holes or a torn section of panel skin around the bracket are all easy to see with the door shut.

   What we do

   We replace the arm and the clevis hardware, then fit a reinforcement strut across the top panel where the skin has torn. A single panel is not designed to take that load on its own, and a strut spreads it across the full width so the same failure does not repeat.

6. 6

   Roller door motor spinning free of the barrel

   Roller door openers drive the barrel directly or through a chain to a driven ring. Some models include a manual override that winds the drive out of engagement. If that override has been left out, or the driven ring has cracked, the motor turns and the curtain stays put.

   What you can check

   Look at the motor head at the end of the barrel. Check whether the manual override handle or chain has been left in the disengaged position, then watch the barrel while someone runs the opener from the wall button.

   What we do

   We re-engage or replace the override mechanism, fit a new driven ring or drive chain where the original has cracked, and reset the open and close limits. Roller door limits sit on cams inside the head, so they always need re-setting after this repair.