Openers fail in a small number of predictable ways, and the symptom is usually enough to identify the culprit. This is the diagnostic path we work through on the phone, so if you can tell us which of these describes your door, we can normally quote the repair before anyone drives anywhere.
The motor runs but nothing moves
Almost always a stripped drive gear.
On chain and belt drive openers there is a plastic gear inside the motor head that meshes with a worm gear on the motor shaft. It is deliberately the weakest component in the chain, designed to strip rather than let the motor burn out. When it goes, the motor spins freely at full speed and the trolley does not move. Sometimes you can see plastic shavings in the housing.
A gear kit is a routine repair and considerably cheaper than a new opener. On a unit that is otherwise sound, it is well worth doing.
The other possibility, less common, is that the trolley has been disconnected — someone pulled the red release cord and it has not been re-engaged. Worth checking first because it costs nothing.
The door starts down, then reverses back up
The photo-eye safety sensors, in the great majority of cases.
Look at the small LEDs on the two sensors near the floor. Two steady lights is what you want. One steady and one flickering or dark is the classic signature of a misalignment. Causes are mundane — a bike knocking a bracket, a snow shovel, a bin, dust and salt film on the lenses, or late-afternoon sun striking the receiver.
If the sensors check out, the next suspects are the down-limit setting (the opener thinks the floor is an obstruction) and the down-force setting. Both are adjustable at the motor head.
One caution: if the fix seems to be winding the force setting up, stop. That setting exists so the door reverses when it meets something soft. Increasing it to force the door closed defeats the safety system, and something mechanical has changed that ought to be found instead.
The motor hums but does not turn
Usually a failed capacitor. The capacitor provides the starting kick for an AC motor; without it the motor energises but cannot begin to rotate, which produces exactly that hum.
It is an inexpensive part. On an older unit, though, it is worth asking what else is tired before committing to the repair.
The other cause is a seized or jammed door — if the door is frozen to the slab or the track is obstructed, the motor is trying to move something that cannot move. Disconnect the opener and try the door by hand before assuming the fault is electrical.
The remote works but the wall button does not
That isolates the fault to the wired circuit rather than the receiver: a broken or shorted low-voltage wire between the wall control and the motor head, a failed wall button, or a loose terminal.
The wire is thin and gets nicked by tools, chewed by rodents, or pulled at a staple. Inexpensive to repair and not a sign the opener is failing.
The wall button works but the remote does not
The reverse case, and it usually means the remote, not the opener.
Start with the battery — it is the answer more often than anything else. Then try reprogramming the remote to the unit. If a second remote also fails after the first has been reprogrammed, the receiver logic board or the antenna wire hanging from the motor head are the next candidates. That antenna wire should hang down freely; tucked up into the housing, range drops dramatically.
Interference is real but over-diagnosed. LED bulbs in the opener itself are a genuine and common cause — some cheap LEDs emit enough radio noise to cut remote range to a few feet. If your remote stopped working shortly after you changed the bulbs, change them back or fit LED bulbs rated for garage door openers.
The door reverses right when it touches the floor
Distinct from reversing partway down, and usually the down-limit rather than the sensors. The opener believes it has hit an obstruction at exactly the point it has reached the floor.
If adjusting the limit does not hold, look at worn rollers binding in the track and at door balance. A door that has gone out of balance changes the resistance the opener sees and pushes settings out of range.
It works intermittently
The hardest one, and the honest list of suspects is longer: a failing logic board, a loose connection at a terminal, a wall control with an intermittent short, thermal cutout on a motor that is overheating because it is fighting an unbalanced door, or radio interference on the remote circuit.
Intermittent faults on an older unit are often the point at which repair stops being economic, because diagnosis takes longer than the parts are worth.
The lights on the motor head are blinking
On LiftMaster and Chamberlain units, blink patterns are diagnostic codes. Counting the blinks and looking them up in the manual is usually the fastest route to an answer. A continuous flashing that will not clear most often points at the safety sensors again.
Before you decide it is the opener
A large share of calls that come in as opener problems turn out to be door problems. If the springs are worn or the door is out of balance, the opener is being asked to lift far more than it was built for and responds by straining, stopping and reversing. Replacing the opener in that situation buys you a new opener that fails the same way.
The test takes thirty seconds: pull the red release cord, lift the door by hand to waist height, let go. If it does not stay put, the springs are the problem and the opener is the victim.
When replacement is the honest answer
- No photo-eye sensors — pre-1993, replace regardless of condition.
- Fixed code rather than rolling code — pre-1996, replace on security grounds.
- Over fifteen years old with a failed logic board — parts support is usually gone.
- Two major components failed at once — gear and board, say.
Otherwise, most opener faults are worth repairing. Opener and motor work is our specialty, and we diagnose before recommending replacement rather than defaulting to the simpler sale.
Tell us what yours is doing — the sound, where it stops, whether the motor runs — and we can usually name the part over the phone. We cover Westmont, Downers Grove, Hinsdale, Darien and eleven other towns in DuPage County.