Why does my garage door opener run but not open the door?

The three most common causes when the motor runs but the door doesn't move: (1) the emergency cord was pulled and the trolley is disconnected from the carriage, (2) the torsion spring is broken and the motor can't lift the unassisted door weight, (3) the plastic drive gear inside the opener is stripped. Lift the door manually — if it's very heavy, the spring is broken.

How do I know if my garage door drive gear is stripped?

A stripped drive gear often produces a grinding or clicking sound as the motor runs — the motor is spinning but the gear teeth slip. There's also a burning plastic smell in some cases. The trolley (carriage on the rail) doesn't move even though the motor is clearly running at full speed.

How much does it cost to replace a garage door drive gear?

Drive gear replacement for LiftMaster or Chamberlain openers costs $150–$220 in NYC, including parts and labor. The repair requires opening the motor housing and is not a DIY job for most homeowners. The fix typically takes 45–60 minutes.

Can a broken spring cause the opener to run without moving the door?

Yes. When a torsion spring breaks, the door weight is no longer counterbalanced. The opener motor runs at full power but can't overcome the full 130–300 lb door weight. The motor may run for its full travel time, trip the thermal overload, or simply stall. The diagnosis: manually try to lift the door — if it's very heavy, the spring is broken, not the opener.

← Back to Blog · 2026-05-04

Garage Door Opener Runs But the Door Won't Move — Exact Diagnosis

Quick Answer — Check These 3 Things First

1. Emergency cord disconnected (trolley not engaged). 2. Broken spring (motor can't lift the unassisted weight). 3. Stripped drive gear (grinding sound, motor spins but carriage doesn't move). Try lifting the door manually — if it's very heavy, the spring is broken.

Cause 1: Emergency Release Cord Is Pulled

The most common and easiest fix. If someone pulled the red emergency cord to manually operate the door and didn't re-engage the trolley, the motor will run the full travel length without moving anything. You'll hear the motor running smoothly and see the drive belt or chain moving — but the trolley carriage just sits there.

Fix: With the door fully closed, pull the red cord toward the motor unit (not straight down — that's how you disconnect it). You'll feel it re-engage. Alternatively, press the wall button — on most modern LiftMaster and Chamberlain units, the carriage re-engages automatically when the motor cycles.

Cause 2: Broken Torsion Spring

This is the most serious cause. When a torsion spring snaps, the door weight is no longer counterbalanced — the opener is trying to lift 130–300 lbs without the spring doing its half of the work. Some openers stall immediately; others groan and push the door a few inches before tripping the thermal overload.

Diagnosis: Pull the red cord to disconnect the opener. Try to lift the door by hand from the bottom. If it's extremely heavy — heavier than you'd expect from lifting a door — the spring is broken. Look above the door above the closed door; a broken torsion spring will often show a visible gap in the coils or a coil that's dropped to one side of the shaft.

Fix: This is not a DIY repair. Call a technician. Spring replacement in NYC: $280–$520 for a matched pair. Same-day service available.

Cause 3: Stripped Drive Gear

The drive gear is a plastic helical gear inside the opener motor housing that transfers power from the motor shaft to the drive belt or chain. Plastic gears wear over 10–15 years of cycling and can strip suddenly — especially if the door was binding (from a broken spring, off-track roller, or stiff hardware) that caused the motor to work harder than rated.

Diagnosis: Listen while the motor runs. A stripped gear produces a high-pitched grinding or clicking sound. The motor sounds like it's running freely (no load resistance), and the drive mechanism (belt or chain) doesn't move. Open the light cover on the motor unit and shine a light inside — you can sometimes see plastic shavings or a visibly damaged gear tooth profile.

Fix: Drive gear replacement costs $150–$220 in NYC for most LiftMaster and Chamberlain models. Genie gear kits are similar. If the opener is over 12 years old, a full replacement ($399–$480) is usually better value than a gear repair.

Cause 4: Snapped Belt or Chain

Less common but possible. A belt-drive opener's rubber belt can snap; a chain-drive's chain can break or jump off the sprocket. Visually inspect the rail — if the belt or chain is hanging loose or not running between the motor unit and the trolley, that's the issue. Belt replacement: $100–$150 with labor. Chain repair/replacement: $80–$130.

What to Do Right Now

Pull the red cord to disconnect the opener from the door.
Try lifting the door manually. Normal weight = opener issue. Very heavy = spring issue.
If it's the opener (door lifts normally by hand), call for same-day opener repair.
If the door is very heavy, call for spring replacement — do not use the door.

Need same-day diagnosis and repair?

OnPoint Pro Doors — NYC, Long Island, NJ. Written quote before work starts. ★ 4.9 / 5 (287+ reviews).

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