Garage Door Won't Open? How to Diagnose and Fix It
1. Diagnose: What's Happening?
| Symptom | Likely Cause | DIY? |
|---|---|---|
| Door starts down then reverses | Safety sensor misaligned or dirty | Yes — free |
| Motor runs, chain moves, door doesn't budge | Broken spring | NO — call pro |
| Motor runs, chain does NOT move | Stripped gear in opener | Yes — moderate |
| Nothing happens when pressing button | Dead remote/wall button, or power issue | Yes — check power |
| Door is heavy or crooked manually | Broken spring or off-track | NO — call pro |
2. Fix: Safety Sensors (Free, 5 Minutes)
- Wipe both sensor lenses with a clean cloth (dust and cobwebs block the beam).
- Check that both sensors face each other and show solid lights (blinking = misaligned).
- Adjust the brackets by hand until the LED turns steady.
- Check sensor wires for damage near the bottom of the tracks.
- Test the door.
3. Fix: Stripped Opener Gear ($20–$40 DIY)
If the motor runs but the chain/belt doesn't move, the internal drive gear is stripped. Common on openers over 10 years old.
- Unplug the opener.
- Remove the cover — you'll likely see white plastic shavings inside (dead giveaway).
- Remove the old gear assembly.
- Install the new gear kit and apply fresh grease.
- Reassemble and test.
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Get Your Free Diagnosis4. Products
LiftMaster 41A2817 Gear and Sprocket Kit — ~$25 — View at Home Depot
Blaster Garage Door Lubricant — ~$6 — View at Home Depot
5. Cost Breakdown
| Repair | DIY Cost | Pro Cost |
|---|---|---|
| Sensor clean/realign | $0 | $75–$150 |
| Gear replacement | $20–$40 | $150–$300 |
| Spring replacement | Do NOT DIY | $150–$350 |
| Full opener replacement | $150–$250 | $300–$700 |
FAQ
Why does my garage door go down then back up?
Almost always misaligned safety sensors. Clean the lenses and adjust until both show solid lights (not blinking).
How do I know if my garage door spring is broken?
Look at the torsion spring above the door (the long coiled rod). If you see a gap (2–3 inches where it snapped), it's broken. The door will also feel extremely heavy if you try to lift it manually.
Can I open my garage door with a broken spring?
You can use the emergency release cord and lift manually, but the door will be very heavy (150–250 lbs without spring assist). Get it repaired before using the opener again.
Frequently Asked Questions
Why won't my garage door open?
Check these in order: dead remote batteries, the wall switch, the photo-eye sensors (small lights at the bottom of the tracks, must be aligned), and the manual release handle. If the motor runs but the door does not move, the drive gear or belt is likely broken.
How much does garage door repair cost?
Remote batteries: $5. Sensor realignment: free (DIY). Spring replacement: $200 to $400 (hire a pro, springs are dangerous). Opener replacement: $200 to $500.
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