It is one of the more confusing garage door faults, because everything sounds like it is working. You press the button, the motor runs for a few seconds, the light comes on, and the door sits exactly where it was. Nothing is obviously broken and nothing is obviously wrong.

What has almost always happened is that the connection between the motor and the door has been lost somewhere along the chain — and there are four very different places that can happen. Two are trivial. Two are dangerous to touch. Telling them apart takes about five minutes and no tools.

First, a safety note worth taking seriously

A residential garage door weighs well over a hundred pounds, and the springs above it store enough energy to cause serious injury when they are released without control. Nothing below asks you to touch a spring, a cable, or the bottom bracket. If the diagnosis lands on any of those, that is where the do-it-yourself part stops — not out of caution for its own sake, but because those components fail suddenly rather than gradually.

The four-step diagnosis

1. Check whether the trolley has been disconnected

Every opener has an emergency release — usually a red cord hanging from the carriage that runs along the rail. Pulling it disengages the door from the opener so the door can be operated by hand during a power failure. It also gets pulled by accident, by tall boxes, by kids, and by anyone who was told once that this is what you pull when the door is stuck.

Look along the rail while someone runs the opener. If the carriage travels back and forth along the rail on its own and the door does not follow, the trolley is disengaged. Re-engaging is usually a matter of pulling the release cord back toward the door, or running the opener once so the carriage re-latches. This is the best outcome on the list and it costs nothing.

2. Check for a broken spring

Close the door fully and disconnect the opener at the release. Then lift the door by hand, about a foot.

A balanced door feels like lifting maybe ten pounds, and it stays roughly where you leave it. A door with a broken spring feels like lifting the whole door, because you are. If it slams back down when you let go, or if you cannot lift it at all, stop there.

Look at the torsion spring on the shaft above the opening. A broken torsion spring shows an unmistakable gap of a couple of inches where the coil has separated, and the two broken ends are usually visibly out of line. On an extension-spring door, look along the tracks at each side instead.

When a spring goes, the motor is trying to lift a weight it was never designed to lift, and the gear inside the opener is the part that gives up next. That is why a broken spring often produces two repairs instead of one if the opener keeps getting used. Garage door spring repair is the classic case for not waiting.

3. Check the cables and the drums

If the springs are intact and the door still will not budge, look at the lift cables running from the bottom bracket at each side up to the drums at the ends of the torsion shaft.

What you are looking for: a cable that has come off its drum and is now slack or wound in the wrong place; a cable that has jumped a groove; fraying near the bottom bracket, where water and salt sit; or a door that is sitting visibly crooked, higher on one side than the other. A cable that has come off one drum will usually also have pulled that side of the door out of square, and the door may now be binding in the track as well.

Cables sit under the same tension as the springs. Rewinding a cable onto a drum means controlling the shaft, which means dealing with the springs. This one belongs with garage door cable repair rather than with a ladder and a pair of pliers.

4. Check the opener itself

If the door lifts easily by hand, sits level, holds its position, and the carriage is engaged — then the fault is inside the opener. Three possibilities, distinguishable by sound:

• Motor hums or runs freely with a grinding note, and nothing moves at all. On a chain or belt drive this is usually a stripped drive gear — a plastic gear that wears against the worm gear over years of use. It is a common and repairable failure on an otherwise fine opener.
• Chain or belt moves but the carriage does not travel. The carriage has come loose from the chain, or the trolley assembly itself has failed.
• Screw drive turns and the carriage stays put. Stripped carriage threads, or the drive tube has lost its coupler.

None of these require touching a spring, but all of them require opening the head unit, and whether it is worth repairing depends on the age of the unit and whether parts are still available for it. That judgment is the useful part of a garage door opener service call.

What not to do while you are working it out

The single worst response to this fault is to keep pressing the button. If a spring is broken, every attempt loads the opener gear against a weight several times what it was rated for. If a cable is off a drum, every attempt winds the door further out of square and can pull rollers out of the track entirely. If the gear is already stripped, repeated attempts turn a gear replacement into a burned-out motor.

The second worst is forcing the door up by hand when it does not want to move. A door that is binding in the track is being held by something, and that something is usually a roller that has left the track or a cable that has gone slack. Forcing it can bend the track or drop the door.

How to tell a spring problem from an opener problem in one test

If there is one thing to take away, it is this: disconnect the opener and lift the door by hand.

Lifts easily and stays put — the door and the springs are fine, and the problem is electrical or mechanical inside the opener. Heavy, or falls when released — the problem is the springs or the cables, and the opener is a victim rather than the cause. That single test sorts the cheap repairs from the ones that need a technician, and it costs nothing but a minute.

Frequently asked questions

The motor runs for a few seconds then stops. Is that the same fault?

Often, yes. Many openers cut power when they do not see the expected movement within a set time. A short run followed by a stop is the opener protecting itself, and it points at a mechanical disconnection rather than an electrical fault.

Can I still use the door manually if the opener has failed?

If the springs are intact, yes — pull the release and operate it by hand. If the springs are broken, no. A door that is not spring-balanced is dangerous to lift, and holding it open with a prop is not a safe arrangement.

Does a stripped gear mean I need a whole new opener?

Not necessarily. Drive gear kits exist for many common openers and a gear replacement on a sound unit is a reasonable repair. Age, availability of parts, and whether the unit has modern safety features all factor into whether it is worth doing.

Both springs look fine but the door is heavy. What else could it be?

A spring that has lost tension without visibly breaking, a door that has gained weight from water absorption in wood panels, seized rollers, or a track that has shifted. All of it shows up in the same lift-by-hand test.

Why did this happen with no warning?

There usually was warning, just not a loud one. Springs make a distinct bang when they go, but before that the door often gets slightly slower or noisier. A cable frays for months before it lets go. The five-minute check above, done twice a year, catches most of it early.