When my house was new, in the summertime, the garage
door (on the north side of the house) would not close in the
evening, when the sun was shining on the receiving safety
sensor. Had to get out of the car with the clicker, stand
with my shadow falling on the sensor, and stay there until
the door closed. Other times of the year, no problem, since
the evening sun did not hit the sensor. After a couple of years,
the olive tree grew enough to shade the sensor when the sun
was low in the west. Which may or may not be related to your
problem. See if the lenses on the sensors are dirty, clean
if necessary. Check for sensor alignment issues.
The tech support area of the Chamberlain website
has this to say about safety sensor issues:
If the door will not close unless constant pressure is applied to the
wall button, the symptoms are indicative of a safety sensor issue.
There are a few different things that can cause this type of problem,
so listed below are the issues with their corresponding solutions.
1. Check each sensor for a steady glowing indicator light. If both
indicator lights are on, or if one indicator light is flickering, the
sensors may be slightly misaligned. To check for misalignment; obstruct
the beam of the sensors so that they cannot see each other. When the
beam is blocked, the indicator light on one of the two sensors will
temporarily go out. This is the receiving sensor. Remove the
obstruction and loosen the wingnut on the back of the receiving sensor.
Adjust the receiving sensor until the green indicator light is bright
and steady, then retighten the wingnut. This usually takes a couple of
attempts before it is back in alignment.
2. If an indicator light is out on only one of the sensors, check for a
possible loose wire. Sensor wires are attached to the white and black
terminals on the back or side panel of the overhead motor unit. If
wires are securely connected, check the wires running from the sensor
to the motor unit for any breaks. Check anywhere the wires are spliced
together. Try moving the wire around where it is connected at the back
of the sensor. If the indicator light does not come on, you will need
to replace the sensors.
3. If the problem exists only during the daytime, check to make sure
the receiving eye is not in direct sunlight. If this is the case, it
may be necessary to remount or adjust the sensor back toward the side
wall of the garage.
Hope this helps,