My garage door opener hums or buzzes but the door won't move. What's wrong?

When a garage door opener hums or buzzes but the door does not move, it means the motor has power but cannot drive the door. The hum is the motor trying and failing. The four usual causes are a failed capacitor, a stripped drive gear, a door that is locked or frozen to the floor, and a broken spring that overloads the motor. The smartest first step is to disconnect the opener with the emergency release and check whether the door moves freely by hand, which quickly separates a door problem from an opener problem. Here is how to track down the cause.

First, separate the door from the opener

Before blaming the opener, find out if the door itself is the problem. Pull the emergency release cord, the red handle hanging from the opener rail, to disconnect the door from the motor. Then try to lift the door by hand. This one test tells you a lot.

If the door will not budge or feels extremely heavy by hand, the problem is the door, not the opener. It may be locked, frozen to the floor, jammed on the track, or held down by a broken spring. The opener was humming because it was straining against a door it could not lift. In that case, fixing the door is the answer, and forcing the opener would only damage it.

If the door moves freely and smoothly by hand and stays where you put it, the door is fine and the problem is inside the opener. The motor has power, hums, but cannot turn the drive. That points to an internal fault like a bad capacitor or a stripped gear. Knowing which side of this line you are on saves a lot of guesswork.

If the door is stuck: locks, ice, and springs

If the hand test showed a stuck door, work through these. First, check the locks. Many doors have a manual slide lock or a handle lock that, if engaged, bolts the door to the track. An opener humming against a locked door is common. Make sure no lock is thrown and no vacation-mode lock on the wall console is on.

Next, in a Colorado winter, check whether the door is frozen to the floor. Melted snow under the bottom seal can freeze overnight and glue the door to the concrete. The opener hums and strains but the door will not break free. Never force it; chip the ice gently or pour warm (not boiling) water along the bottom seal to release it, then operate the door.

Finally, suspect a broken spring. If the door is not locked or frozen but is still impossibly heavy by hand, a spring has likely snapped, dropping the full weight onto the opener. Look at the torsion spring above the door for a visible gap. The Consumer Product Safety Commission warns that springs store dangerous energy, so do not attempt a spring repair yourself; leave the door down and call a technician.

If the opener is at fault: capacitor and gear

If the door moves freely by hand, the fault is inside the opener. The most common electrical cause is a failed capacitor. The capacitor is a small cylinder that gives the motor the jolt it needs to start turning. When it fails, the motor gets power and hums or buzzes but cannot start spinning. A bad capacitor is a frequent cause of this exact symptom and is a part-level repair best done by a technician, since capacitors can hold a charge.

The other common opener cause is a stripped drive gear. The main plastic gear can wear out so the motor spins (or strains) without driving the chain, belt, or screw. With a stripped gear you often see white plastic shavings near the motor, and the motor may run rather than just hum. Either way, the link between the motor and the door is broken.

Hand test result	Likely cause
Door very heavy, gap in spring	Broken spring
Door won't move, lock engaged	Manual or vacation lock
Door stuck at floor in winter	Frozen to the ground
Door moves freely, motor hums	Bad capacitor or stripped gear

Both the capacitor and the gear are internal repairs. On a newer opener they are worth fixing; on a very old unit, replacement may cost about the same and get you modern features. A technician can test the capacitor and inspect the gear to tell which it is.

What to do next, safely

Start with the hand test, because it instantly narrows the problem. Then check the easy door causes: unlock any slide or vacation lock, and free the door if it is frozen down. These you can safely handle yourself, and they resolve a good share of humming-but-not-moving cases without any parts.

Do not keep pressing the button while the opener hums. Repeatedly straining the motor can burn it out or worsen a stripped gear, turning a small fix into a bigger one. If the opener hums for more than a second or two without the door moving, stop and diagnose rather than retry.

While the opener is disconnected, you can still use the door manually. With the emergency release pulled and the door free to move by hand, you can open it to get a car out, then close it, so you are not trapped while you wait for a repair. Just be sure the door is balanced and not held by a broken spring before you do this, because a door with a failed spring is heavy and can drop. If the door is heavy or will not stay up, leave it down and do not try to prop it open.

For the internal causes, a broken spring, bad capacitor, or stripped gear, call a technician. These involve stored energy or precise parts and are not safe or practical as DIY jobs for most homeowners. A pro can test the capacitor, inspect the gear, check the springs, and fix the real cause in one visit.

The repair-or-replace math depends on the opener's age. A capacitor or gear kit is an inexpensive part, so on an opener under about 10 years old, fixing it is the clear choice. On a unit pushing 15 years, the same repair buys time on a machine that is near the end of its life anyway, and replacement gets you a quieter drive, battery backup, and smartphone control for a few hundred dollars. A technician can give you both numbers so the decision is easy.

A little prevention reduces how often you meet this problem. Keep the door balanced by having the springs checked during a tune-up, since a strained opener is what cooks capacitors and strips gears early. Lubricate the door's moving parts twice a year so the opener is not fighting friction. And in winter, clear snow and ice from the bottom seal so the door never freezes down and forces the motor to hum against a stuck door. These habits keep the opener doing the light work it was designed for. G Brothers offers same-day garage door and opener repair across the Denver metro, with free estimates.