Garage Door Not Opening But Motor Is Running
When the garage door opener motor runs its full travel but the door doesn't budge, the motor itself is fine — the problem lies in the mechanical link between the opener and the door. The most common cause is a broken torsion spring, which counterbalances the door's weight and makes it possible for the opener to lift it. Without a working spring, the opener can't generate enough torque to raise a 150–300 lb door. Other causes include a snapped lift cable, a stripped drive gear inside the opener, the trolley carriage disconnected from the door, or the door derailed off its track. This guide walks you through safe visual diagnosis — but if you confirm a broken torsion spring, STOP and call a professional. Torsion springs store enormous mechanical energy and have caused severe injuries and fatalities when mishandled.
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Common Symptoms
- Motor runs a full up or down cycle but door doesn't move at all
- Loud bang from the garage (spring snapping) followed by door failing to open
- Door moves 2–4 inches then stops and reverses
- Door feels extremely heavy when you try to lift it manually
- Opener makes a grinding or clicking sound rather than a smooth hum
- Trolley carriage slides on the rail but door stays down
- Slack or coiled cable visible on one or both sides of the door
Most Likely Causes
- 1
Broken Torsion Spring (Most Common — Call a Pro)
The torsion spring sits horizontally above the garage door on a steel shaft. It stores mechanical energy when the door is closed, releasing it to counterbalance the door's weight when opening. When the spring breaks — usually with a loud bang — the opener motor cannot lift the full unassisted weight of the door. Look above the center of the door: a broken torsion spring will have a visible gap of 1–2 inches where it snapped. DO NOT attempt to replace a torsion spring yourself — the spring is wound under hundreds of foot-pounds of torque and can release violently if handled incorrectly.
- 2
Snapped or Slack Lift Cable
Steel lift cables run from the bottom corners of the door up to a drum at each end of the torsion spring shaft. If a cable snaps or jumps off the drum, one side of the door loses its lift, causing it to tilt, bind, and fail to open. You'll see a coiled or dangling cable on one side. Cable replacement is a moderately advanced DIY repair but is much safer than spring work since the cable itself carries no stored energy — however, the spring is still under tension during cable work, so professional service is still recommended.
- 3
Stripped Drive Gear in Opener
Chain-drive and screw-drive openers use a plastic nylon drive gear that meshes with the motor's worm gear. This plastic gear wears and strips over time, especially if the door is heavy or the springs are weak. When the gear strips, the motor spins freely but the drive sprocket doesn't turn — you'll hear a grinding or whirring sound instead of the normal drive noise. The gear-and-sprocket kit is a $20–40 part and a legitimate DIY repair on most Chamberlain, LiftMaster, and Genie openers.
- 4
Trolley Carriage Disconnected
Every opener has a red emergency release cord hanging from the trolley carriage on the rail. Pulling this cord disconnects the carriage from the drive belt or chain so you can open the door manually during a power outage. If someone pulled the release cord and the carriage was never re-engaged, the motor will run the trolley back and forth while the door stays still. Re-engaging is simple: pull the release cord toward the door (not straight down), then manually lift the door until the carriage snaps back onto the drive mechanism.
- 5
Door Off Track or Binding
If a roller has jumped out of the vertical track, the door will bind and the opener's auto-reverse safety will stop the door after a few inches of travel. Look for a bent or misaligned track section, a roller out of its channel, or a dented door panel that's catching on the frame. Minor track alignment issues are DIY-repairable; severely bent tracks or damaged panels usually require a garage door service technician.
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Quick DIY Checks
TORSION SPRING REPLACEMENT IS NOT A DIY REPAIR. Torsion springs are wound under hundreds of foot-pounds of stored energy. An improperly wound or handled spring can snap and release with enough force to cause severe lacerations, broken bones, or death. ALWAYS hire a licensed garage door technician for spring replacement. This warning is non-negotiable.
Never attempt to manually lift a garage door with a broken torsion spring. Without the spring's counterbalance, the door weighs its full 150–300 lbs and can drop suddenly, crushing anything beneath it. Keep people and vehicles away from the door area until the spring is repaired by a professional.
Do not bypass the auto-reverse safety by cranking the force setting to maximum. The auto-reverse is a required safety feature. If the door won't stay closed without maximum force, the problem is mechanical (spring tension, track friction, cold weather) — not force setting deficiency.
Unplug the opener before performing any repair inside the opener head (gear replacement, logic board work). The motor can activate if someone presses the wall button while you have your hands inside the unit.
- 1SAFETY FIRST — Do NOT pull the emergency release cord yet. Before anything, look through the small window in your garage door (or go inside if it's safe to do so) and visually inspect the torsion spring above the door. The torsion spring is the large coiled spring mounted horizontally on a shaft above the door. A broken spring will have a visible gap of 1–2 inches in the middle of the coil where it snapped. If you see a gap: the spring is broken. STOP all repair attempts immediately and call a licensed garage door company. Do not attempt to open the door manually — a door without a working spring can fall rapidly and cause serious injury.
- 2Check the cables: Look at both lower corners of the garage door where the steel lift cables connect. A healthy cable runs taut from the bottom bracket up to the drum at the top of the door frame. If you see a coiled pile of cable on the floor, or a cable dangling loose on one side, the cable has snapped or jumped off the drum. Cable issues are safer than spring issues but still involve spring tension — professional repair is strongly recommended.
- 3Check the trolley carriage disconnect: Look at the trolley carriage — the metal block that slides along the opener rail above the door. Does the red emergency release cord hang from it? If the carriage is disconnected (someone pulled the cord earlier), the drive bar from the trolley to the door bracket will be unlatched. To re-engage: pull the red cord toward the motor (parallel to the ceiling, not downward) — this re-arms the spring latch inside the carriage. Then open the door manually until you hear a click as the carriage catches the drive chain or belt. Test with the wall button.
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Try Pro — $7.99/mo- 4Listen carefully to the motor sound: Run the opener and listen. A normal opener makes a steady mechanical hum with the chain or belt moving. A stripped drive gear makes a high-pitched grinding or whirring noise as the motor spins but the drive doesn't engage. If you hear grinding with no chain/belt movement visible through the rail cover, you likely have a stripped gear. Order a gear-and-sprocket kit for your opener model (search your opener's model number + 'gear sprocket kit').
- 5Check for door obstruction or track problem: If the door moves 2–6 inches and then stops and reverses, the opener's auto-reverse (force limit or obstruction sensor) is triggering. Inspect the vertical tracks on both sides for bent sections, loose mounting brackets, or a roller that has jumped out of the track. Also check the photo-eye safety sensors at the bottom of the door frame — a misaligned sensor (blinking amber LED) will cause the door to reverse immediately when closing or refuse to open if wired incorrectly.
- 6Test manual operation (ONLY if spring is confirmed intact): With the spring confirmed unbroken and cables intact, pull the emergency release cord straight down to disconnect the opener. Try lifting the door manually with both hands. A properly spring-balanced door should lift smoothly and stay up when raised to waist height with just light pressure. If the door is extremely heavy (requires serious effort) or one side is higher than the other, the spring tension is unbalanced or one spring has weakened. Call a professional.
- 7Replace a stripped drive gear (DIY-appropriate repair): If you've confirmed the gear is stripped, unplug the opener. Remove the light cover and access panel from the opener head. Photograph the gear assembly before disassembly. Remove the old nylon gear by extracting the retaining cotter pin or snap ring on the gear shaft. Slide out the worn gear, clean the worm gear shaft, apply a thin coat of white lithium grease, and install the new gear-and-sprocket kit. Reassemble in reverse order. Most Chamberlain/LiftMaster gear kits include the sprocket, gear, and cotter pin.
- 8Test limit and force settings (door reverses mid-travel): If the door moves partway and reverses without obstruction, the opener's force or travel limit settings may need adjustment. On belt-drive openers, there are typically two adjustment screws on the back or side of the motor head labeled 'UP Force' and 'DOWN Force' (or 'UP Limit' and 'DOWN Limit'). Consult your opener manual — small clockwise turns increase force. However, increasing force too much can override the auto-reverse safety and create a hazard. First confirm the spring is properly tensioned before adjusting force settings.
- 9Re-engage and test: After any repair, reconnect the trolley carriage to the drive mechanism, restore power, and run three full open/close cycles. Watch the door travel for smooth, even movement on both sides. Confirm the auto-reverse safety works: place a 2x4 flat on the ground in the door's path and close the door — it should reverse when it contacts the board. If it doesn't reverse, adjust the down-force immediately or call a technician.
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Repair vs Replace
Most garage door motor-runs-but-door-won't-move failures are repairable at reasonable cost. A broken torsion spring is $150–350 professionally replaced and should last 7–12 years. A stripped drive gear is a $20–40 DIY part. Only consider replacing the opener if it's over 15 years old, lacks auto-reverse safety, or the logic board has failed alongside the mechanical issue.
Est. Repair Cost
$150–$350 (professional spring replacement) — $20–$40 (DIY drive gear kit) — $80–$200 (professional cable repair)
Est. Replacement Cost
$600–$1,500 for a new garage door opener — $800–$2,500 for a new door
Recommended Tools & Parts
- Buy on Amazon →
Torsion Spring Replacement (Professional Service)
Torsion springs must be replaced by a licensed garage door technician. Springs are ordered by wire diameter, inside diameter, and length — the technician will measure and source the correct spring. Do not order springs yourself for DIY installation.
$150–$350 installed (professional)
- Buy on Amazon →
Drive Gear and Sprocket Kit
Nylon replacement gear for chain-drive or belt-drive openers. Compatible with most Chamberlain, LiftMaster, Craftsman, and Sears openers. Order by opener model number for exact fit. Includes nylon gear, sprocket, and cotter pin.
$20–$40
- Buy on Amazon →
Garage Door Lift Cable
1/8-inch galvanized steel lift cable for standard residential garage doors. Sold in pairs. Connects door bottom bracket to winding drum. Replace both cables at the same time for even wear.
$15–$30 (pair)
- Buy on Amazon →
White Lithium Grease Spray
Lubricant for the torsion spring shaft, roller bearings, and drive gear. Do not use WD-40 on garage door components — it degrades rubber seals and attracts dirt. Use white lithium grease or dedicated garage door lubricant.
$8–$15
Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.
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Frequently Asked Questions
- Can I open my garage door manually if the spring is broken?
- You should not attempt to lift a garage door with a broken torsion spring. Without the spring's counterbalance, the door weighs its full 150–300 lbs. Attempting to lift it risks the door falling suddenly and crushing you or your vehicle. If you must get your car out, call a garage door company for emergency service — most offer same-day appointments for broken springs.
- How do I know if it's the spring or the opener gear that's broken?
- Visual inspection tells you quickly. Look above the center of the door at the horizontal torsion spring — a broken spring has a visible 1–2 inch gap where it snapped. If the spring looks intact (no gap), listen to the opener: a steady grinding or whirring with no chain/belt movement points to a stripped drive gear. You can also try manual operation: disconnect the trolley and try lifting the door by hand. If it's extremely heavy (more than 10 lbs of effort), the spring is broken or weak.
- My garage door moved 2 inches then reversed — what's wrong?
- The opener's auto-reverse safety triggered. Check: (1) The photo-eye sensors at the bottom of the door frame — the sending eye (amber LED, always lit) and receiving eye (green LED, lit when aligned). A blinking green LED means misalignment — adjust the sensor bracket until it stays solid. (2) The door track for binding, bent sections, or a roller off the track. (3) The down-force setting — but only adjust this if the track and sensors check out, as over-forcing bypasses a critical safety feature.
- How long do garage door torsion springs last?
- Standard torsion springs are rated for 10,000 open/close cycles — roughly 7–10 years for a door used 4–5 times daily. High-cycle springs (25,000 or 100,000 cycles) cost more but dramatically reduce replacement frequency. When one spring breaks, replace both at the same time — the other spring has the same wear and will likely fail within months.