Your garage door won't close in the afternoon sun. Here's why, and what to do
If the door opens fine but refuses to close when the sun hits the garage, the safety sensors may be the reason. Here is what the opener manual says to check and what it says to do about sunlight.
Some days the door closes fine. Then, around the same time every afternoon, you press the button and the lights on the opener blink and the door stays open, or starts down and goes back up.
Our view: that pattern is worth noticing. A door that fails at the same time each day and works the rest of the time points toward sunlight on the sensors.
We quote the Chamberlain B980 manual below. Other models differ, so check yours.
What the opener manual says is happening
The Chamberlain B980 manual, page 28, says: "When the light beam is obstructed or misaligned while the door is closing, the door will reverse and the garage door opener lights will flash ten times. If the door is already open, it will not close."
The B980 manual, page 22, describes the two sensors: "The sending sensor (with an amber LED) transmits an invisible light beam to the receiving sensor (with a green LED)." "The lenses on both sensors should point toward each other."
Rule out the ordinary causes first
If the green light on the receiving sensor is not glowing, the B980 manual, page 28, gives two checks: "Make sure the sensor wire is not shorted/broken." "Make sure the sensors are aligned." It says "The LEDs in both sensors will glow steadily if they are aligned and wired correctly." and "The sensors can be aligned by loosening the wing nuts, aligning the sensors, and tightening the wing nuts."
Our advice: clear anything sitting in front of either sensor first, and leave a cut or damaged wire to a technician.
After any change, the B980 manual, page 34, puts it in capitals: "Safety reversal system MUST be tested every month." "After ANY adjustments are made, the safety reversal system MUST be tested."
What the manual says to do about sun
If the receiving sensor is in direct sunlight, the B980 manual, page 28, says to switch it with the sending sensor so it is on the opposite side of the door.
Our advice: have a garage door technician do it.
Chamberlain also sells a Safety Sensor Sunblocker Kit, part 041B0873, also known as 41B873, which its page says is used to shield sunlight, listed at $24.99 when we checked on October 15, 2026. Its page says to check the manual for your model before ordering.
Never switch the sensors off
The B980 manual says it in capitals: "This required safety device MUST NOT be disabled" (page 22).
Our advice: do not cover the sensors or take them down. If you cannot get both lights glowing steady, leave the door where it is and call a technician.
Springs and cables are a different job
The B980 manual, page 34, says: "ALL repairs to cables, spring assemblies and other hardware, ALL of which are under EXTREME tension, MUST be made by a trained door systems technician."
Our advice: call a technician for them, and do not try to adjust them yourself.
What to do this week
Our advice:
- Note what time of day the door refuses to close.
- Look at both sensor lights and run the two page 28 checks above.
- If it only fails when the sun hits the receiving sensor, call a technician about moving the sensors, or check your manual for the sunblocker kit.
- After anyone touches the sensors, test the safety reversal. In the B980 manual's words: "Safety reversal system MUST be tested every month." "After ANY adjustments are made, the safety reversal system MUST be tested."
