You press the button to close your garage door. It moves down six inches, stops, reverses back to the top, and the overhead light flashes at you like a strobe light.
You didn’t break it. You just have Misaligned Safety Sensors.
This is the single most common “repair” call in California. Homeowners pay service companies $150 just for a technician to bend a small metal bracket back into place. At CaliforniaGarageDoors.us, we believe you should keep that money. Here is how to fix your sensors yourself in less than 5 minutes.
Table of Contents
The Symptoms: The “10-Flash” Code
Before you grab your screwdriver, confirm this is actually a sensor problem.
On almost all LiftMaster, Chamberlain, and Craftsman openers (the most common brands in CA), the motor has a specific error code for sensors:
- The Symptom: The door opens fine, but refuses to close.
- The Error: When it reverses, the main light bulb on the motor unit flashes 10 times and makes a clicking sound.
If your light is flashing a different number of times (like 5 times), it might be a motor overheating issue. But 10 flashes always means “I can’t see the safety beam.”
Green Light vs. Amber Light
Go down to the bottom of your garage door tracks. You will see two small black boxes (“eyes”) clipped onto the rail, about 6 inches off the ground.
1. The “Sending” Eye (Amber/Yellow)
This sensor sends the invisible infrared beam. It usually has a Yellow or Amber LED light.
Status Check: This light should always be solid. If it is off, you have a loose wire or no power.
2. The “Receiving” Eye (Green)
This sensor catches the beam. It usually has a Green LED light.
Status Check:
- Solid Green: The sensors are aligned. (System is Good).
- Flickering Green: The sensors are almost aligned but vibrating (System is Bad).
- Light Off: The beam is completely broken or blocked (System is Bad).
The 3-Step Alignment Fix
You don’t need special tools—usually just your hands or a small wrench.
Step 1: Clear the Path
This sounds obvious, but check for spiderwebs, leaves, or a broom handle leaning against the track. In California garages, we often see cobwebs accumulate inside the sensor lens hood, blocking the beam.
Step 2: Loosen the Wing Nut
The sensors are attached to the track with a small bracket held by a wing nut.
Action: Loosen the wing nut slightly (don’t take it off) so the sensor can pivot up and down.
Step 3: The “Laser Aim” Game
This is easiest with two people, but you can do it alone.
- Point the Sending Eye (Amber) directly across the garage.
- Go to the Receiving Eye (Green). Move it gently up, down, left, and right until the Green LED turns Solid Bright Green.
- Once the light is solid, hold the sensor steady and tighten the wing nut firmly.
Pro Tip: If you tighten the nut and the light goes out again, the bracket moved while you were tightening it. Hold it tighter!
Don’t Forget to Clean the Lens
Sometimes the alignment is perfect, but the “eye” is dirty.
Road dust, pollen, and car exhaust can create a film on the glass lens. Use a microfiber cloth (like you use for sunglasses) to gently wipe the lens on both sensors. Do not use water or heavy cleaners, as moisture can damage the electronics.
Frequently Asked Questions
How do I close the door if I can’t fix the sensors right now?
You can override the safety system by pressing and holding the wall button (the wired one inside the garage). Hold it down until the door is completely closed. This forces the motor to ignore the sensor error.
Can I mount the sensors higher than 6 inches?
We do not recommend it. Federal law requires sensors to be installed no more than 6 inches above the floor. This height is chosen specifically to detect a small child or pet crawling under the door. Mounting them higher creates a dangerous blind spot.
What if both lights are completely off?
If neither sensor has a light, you likely have a broken wire. Check the wiring at the motor head (on the ceiling) to make sure they haven’t been pulled out. If the wiring looks good, the sensors themselves may have burned out and need replacement.
Video: Visual Guide to Alignment
Watch how to find the “sweet spot” for your sensors.
Is the green light solid but the door STILL won’t close? The problem might be the sun, not the alignment. Read our guide on The Sunlight Problem.