Why Is My LiftMaster Safety Sensor Showing One Yellow and One Green Light?

Problem Description

Your LiftMaster garage door safety sensors show one amber or yellow LED and one green LED. The amber yellow light is on the sending sensor which emits the infrared beam. The green light is on the receiving sensor which detects the beam. A solid amber and solid green means normal operation. If the green light is blinking or off the sensors are misaligned and the door will not close. The opener light may flash 4 times indicating sensor misalignment.

Symptoms

• Amber yellow sensor light solid but green light blinking
• Green receiving sensor light completely off
• Opener light flashes 4 times when trying to close
• Door reverses immediately when closing
• Door starts to close then stops and reverses
• Yellow sending sensor working but door still wont close

Recognize these? Here's what usually causes it.

Common Causes

• Receiving sensor knocked out of alignment with sending sensor
• Obstruction blocking the invisible infrared beam path
• Sensor lenses dirty or fogged reducing beam detection
• Wiring loose damaged or incorrectly connected
• Sensors not at the same height from floor
• Vibration from door operation shifted sensor position

Tools & Requirements

Step-by-Step Solution

1

Understand the LED Indicators

LiftMaster safety sensors have two components. The sending sensor has an amber or yellow LED and emits the infrared beam. The receiving sensor has a green LED and detects the beam. Both LEDs solid means the system is working normally. If the green LED is blinking or off the receiving sensor is not detecting the beam properly.

2

Check for Opener Blink Codes

LiftMaster openers flash the light bulb to indicate problems. Four flashes means the safety sensors are misaligned. One flash indicates wiring problems. Two flashes means a short or reversed wire connection. Count the flashes after pressing the close button to identify the specific issue.

3

Clean the Sensor Lenses

Loosen the wing nut on the receiving sensor bracket. Use a soft dry cloth to clean the lens on both sensors. Dust dirt and garage grime accumulate on the lenses and reduce beam detection. Even light film can cause intermittent green light issues.

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4

Realign the Receiving Sensor

With the wing nut loosened adjust the angle of the receiving sensor while watching the green LED. When the green LED glows steadily and solid the sensor is properly aligned with the sending sensor. Tighten the wing nut and secure the mounting bracket in place.

5

Check Wiring Connections

LiftMaster sensors use black and white wires. The white wires connect to the number 2 or white terminal on the opener. The white wires with black stripe connect to the number 3 or grey terminal. Verify connections are secure and not reversed. Reversed wires cause 2 flash error codes.

Quick Solutions

Still having issues? This is usually the deeper cause below.

Need More Help? LiftMaster Support

Note: The contact information below connects you directly to LiftMaster's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.