When it really is the opener

Often it is not — a broken spring and a frozen seal both present as opener trouble. When the opener genuinely is the fault, it tends to be one of four things.

It hums but nothing moves

The motor is turning and the drive is not. On the majority of units this is a stripped plastic drive gear, and the common reason it stripped is that the opener was asked to pull against something that would not move — a door frozen to the slab, or one with a broken spring. The gear is the part designed to give way first, which is the machine doing its job.

The repair is usually a gear kit rather than a new opener, provided the motor itself is sound.

It runs but the door stays put

The trolley is disengaged from the carriage — someone pulled the release cord. It reconnects by pulling the cord back toward the motor or by running the opener until it latches, depending on the model.

It closes a few inches and goes back up

Almost always the safety sensors. Clean both lenses, check they face each other, and look for a steady light on each. Road grit and cold-weather condensation on the lens are enough to do it.

If the sensors are plainly fine, the close-force setting may be too low for a door that has got stiffer with the cold — which is worth treating as a symptom of the door, not a number to turn up.

It struggles only when cold

A door that opens normally in October and labours in January is telling you about the door rather than the motor. Grease has thickened on the torsion bar and in the rollers, springs have lost a little of their counterbalance, and the opener is making up the difference until it cannot. Turning the force up masks it and wears the gear.

Repair or replace

Gears, sensors, remotes, limit switches and trolleys are all repairs. A motor that has burned out, or a unit old enough that parts are no longer made, is a replacement. The age at which that crossover happens varies by model, so it is a question for whoever is looking at it rather than something to decide in advance.