Chamberlain C870 Owner's Manual page 27

Installation
STEP 16 Aligning the safety reversing sensors
The door will not close if the sensors have not been installed and aligned correctly.
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.
1. Check to make sure the LEDs in both sensors are glowing steadily. The LEDs in both sensors
will glow steadily if they are aligned and wired correctly.
The sensors can be aligned by loosening the wing nuts, aligning the sensors, and tightening the wing
nuts.
Wing Nut
Amber LED
SENDING SENSOR
(invisible light beam)
RECEIVING SENSOR
If the receiving sensor is in direct
sunlight, switch it with sending sensor so
it is on the opposite side of the door.
IF THE AMBER LED ON THE SENDING SENSOR IS NOT GLOWING:
1. Make sure there is power to the garage door opener.
2. Make sure the sensor wire is not shorted/broken.
3. Make sure the sensor has been wired correctly: white wires to white terminal and white/black
wires to grey terminal.
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IF THE GREEN LED ON THE RECEIVING SENSOR IS NOT GLOWING:
1. Make sure the sensor wire is not shorted/broken.
2. Make sure the sensors are aligned.
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Green LED
STEP 17 Ensure the door control is wired correctly
If the door control has been installed and wired correctly, a message will display on the Smart Control
Panel screen.
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