Start With the Obvious: The Sensors
Photoelectric safety sensors are the #1 reason garage doors refuse to close. They are required on all garage door openers manufactured since 1993, and they cause more service calls than everything else combined.
The symptom: You press the close button. The door starts to close, then immediately reverses and the opener light blinks (usually 10 times for a sensor issue).
Where the sensors are: One on each side of the door, mounted 4–6 inches above the floor on the vertical track brackets. They face each other across the door opening. One has a green LED (sender), one has a green or amber LED (receiver).
Check 1: Are the LEDs Lit?
- Both LEDs solid green/amber: Sensors are aligned and working. Problem is elsewhere.
- Receiver LED off or blinking: Misaligned or obstructed. The receiver (the one that blinks or goes dark) is the one that matters.
- Both LEDs off: No power to the sensors. Check the wiring connections at the opener and at the sensors.
Check 2: Is Something Blocking the Beam?
Look between the sensors. Anything in the beam path — a broom, a trash can, a leaf, a spider web across the lens — breaks the beam and prevents closing. Clear it.
Clean the lenses. Dust and cobwebs on the sensor lenses are invisible from across the garage but block the infrared beam. Wipe both lenses with a dry cloth.
Check 3: Are They Aligned?
The sender shoots a beam to the receiver. If they are even slightly misaligned (bumped by a bike, shifted by vibration), the receiver loses the signal.
How to realign:
- Loosen the wing nut on the receiver bracket (the one with the blinking LED)
- Slowly rotate the receiver left and right until the LED goes solid
- Tighten the wing nut
- Test: close the door. If it closes, you are done.
If the receiver will not stay aligned, the bracket may be loose on the track. Tighten the bracket screw, then realign.
If the Sensors Are Fine: Check These Next
Track Obstruction
Something physically blocking the door path — a tool on the track, a bent track section, debris in the roller path.
How to check: With the door open, visually inspect both vertical and horizontal tracks. Look for dents, bends, or objects in the track channel. Run your hand along the track (door open, opener disconnected) to feel for obstructions.
How to fix a minor bend: Use a pair of locking pliers (Vise-Grips) to gently straighten a small bend in the track. For significant damage, replace the track section — a badly bent track will cause ongoing roller problems.
Door Binding in the Tracks
If one side of the door moves faster than the other, the door twists and binds in the tracks. This happens when the rollers are worn, the tracks are out of plumb, or the door is out of level.
How to check: Close the door manually (pull the emergency release cord). If it moves smoothly by hand but binds or reverses when using the opener, the opener is struggling with resistance — not a sensor issue.
Common fix: Replace worn rollers. Nylon rollers ($5–$8 each) are quieter and smoother than the steel rollers that come with most doors. A standard 7-foot door has 10 rollers — $50–$80 in parts.
Limit Switch Problems
The opener has down limit and up limit settings that tell it how far to travel. If the down limit is set too high, the door “thinks” it is closed before it actually reaches the floor, and it reverses.
The symptom: The door closes partway, then reverses. The sensors are fine. No obstructions.
How to fix:
On most Chamberlain/Liftmaster/Craftsman openers:
- Find the limit adjustment screws on the side or back of the motor unit (usually two screws: one for up, one for down)
- Turn the down limit screw clockwise in small increments (1/4 turn at a time)
- Test after each adjustment
- The door should close fully and sit snug on the floor without reversing
On newer openers with digital controls, adjust the travel limits through the menu on the wall console or the MyQ app.
Do not adjust the force settings to fix a travel problem. The force setting controls how much resistance the opener tolerates before reversing. Increasing the force to compensate for a binding door is dangerous — it overrides the safety reversal system.
Force Settings
If the door reverses because it encounters too much resistance (stiff tracks, heavy door, weak springs), the close force setting may be too low.
How to test: Close the door manually from the half-open position. If it takes significant effort to close, the door is too heavy or the springs are weak — the opener is working too hard.
The proper fix: Adjust the springs (see below), not the force setting. Increasing the force to mask a mechanical problem is how people get hurt — the door will not reverse when it hits something.
If you must adjust force (as a temporary measure): Turn the close force screw clockwise slightly. The door should reverse when it encounters 5 pounds of resistance (test with a roll of paper towels on the floor — the door should reverse when it contacts the roll). If it crushes the roll, the force is too high.
Spring Problems (Call a Pro)
Garage door springs counterbalance the weight of the door. When springs weaken or break, the opener has to do all the work — and it is not designed for that.
Torsion springs (mounted above the door opening on a shaft) and extension springs (mounted along the horizontal tracks) are under extreme tension. A torsion spring stores enough energy to cause serious injury or death if it releases unexpectedly.
Signs of spring problems:
- Door is very heavy when lifted manually
- Door opens unevenly or jerks
- Loud bang from the garage (a spring broke)
- Gap in the spring coils (torsion spring — visible separation between coils means it is broken)
Do not attempt to adjust or replace springs yourself. This is one of the most dangerous DIY tasks in home repair. A torsion spring adjustment requires a specialized winding bar and precise technique. One slip sends the bar flying across the garage.
Cost to have springs replaced: $150–$350 for a single torsion spring, $250–$500 for a pair. The springs should be replaced in pairs even if only one broke — the other is the same age and will fail soon.
The Quick Diagnostic Flowchart
| Symptom | Likely Cause | Fix |
|---|---|---|
| Door reverses, light blinks 10x | Sensor issue | Clean, align, or clear beam path |
| Door reverses, no blink | Force or limit issue | Adjust down limit or check for binding |
| Door closes partway then reverses | Down limit too high | Adjust down limit screw |
| Door closes then immediately reverses | Door hitting floor too hard, then reversing | Adjust down limit (less travel) |
| Door very heavy to lift manually | Spring problem | Call a pro |
| Door binds or scrapes | Track or roller issue | Inspect tracks, replace worn rollers |
| Door closes but leaves a gap at floor | Down limit needs adjustment | Turn down limit clockwise |
| Opener runs but door does not move | Disconnected trolley or broken chain/belt | Re-engage trolley or inspect drive |
What You Can Fix Yourself vs. What Needs a Pro
DIY (Safe, Straightforward)
- Sensor alignment and cleaning
- Sensor wiring reconnection
- Limit switch adjustment
- Roller replacement
- Minor track straightening
- Lubrication (spray tracks, rollers, and hinges with silicone spray — not WD-40, which attracts dirt)
Call a Pro (Safety Risk or Specialized)
- Spring adjustment or replacement
- Cable replacement (cables are under tension)
- Track replacement or major realignment
- Opener replacement or motor repair
- Any situation where the door falls quickly when released (springs are not counterbalancing)
Prevention: What to Do Once a Year
Test the auto-reverse: Place a 2x4 board flat on the floor under the door. Close the door. It should reverse when it contacts the board. If it does not, adjust the close force or call a technician.
Test the sensors: Close the door. While it is closing, wave your hand between the sensors. The door should reverse immediately.
Lubricate: Silicone spray on roller bearings, hinge pins, and track surfaces. White lithium grease on the opener chain or belt if applicable.
Check the springs: With the door closed and the opener disengaged, lift the door to the half-open position. It should stay there on its own. If it drifts down, the springs are weakening.
Inspect cables: Look for fraying, kinks, or rust on the lift cables. Frayed cables can snap without warning.
A 10-minute annual check prevents most emergency service calls. And it keeps your door from becoming the one that will not close at 7 AM when you are already late for work.