Diagnostic chart, 3 flashes – Chamberlain SECURITY+ 3265M-267 1/2 HP User Manual
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Your garage door opener is programmed with self-diagnostic 
capabilities. The “Learn” button/diagnostic LED will fl ash a 
number of times then pause signifying it has found a potential 
issue. Consult Diagnostic Chart below.
Diagnostic Chart
Symptom: One or both of the indicator lights on the safety reversing sensors 
do not glow steady.
• Inspect sensor wires for a short (staple in wire), correct wiring polarity
(black/white wires reversed), broken or disconnected wires, replace/attach 
as needed.
• Disconnect all wires from back of motor unit.
• Remove sensors from brackets and shorten sensor wires to 1-2 ft. (30-60 cm)
from back each of sensor.
• Reattach sending eye to motor unit using shortened wires. If sending eye
indicator light glows steadily, attach the receiving eye.
• Align sensors, if the indicator lights glow replace the wires for the sensors. If
the sensor indicator lights do not light, replace the safety sensors.
Symptom: LED is not lit on door control.
• Inspect door control/wires for a short (staple in wire), replace as needed.
• Disconnect wires at door control, touch wires together. If motor unit activates,
replace door control.
• If motor unit does not activate, disconnect door control wires from motor unit.
Momentarily short across red and white terminals with jumper wire. If motor 
unit activates, replace door control wires.
Symptom: Sending indicator light glows steadily, receiving indicator light is 
dim or fl ashing.
• Realign receiving eye sensor, clean lens and secure brackets.
• Verify door track is fi rmly secured to wall and does not move.
Symptom: Motor has over heated; the motor unit does not operate or trolley is 
stuck on stop bolt = Motor unit hums briefl y; RPM Sensor = Short travel 6-8" 
(15-20 cm). 
• Unplug unit to reset. Try to operate motor unit, check diagnostic code.
• If it is still fl ashing 5 times and motor unit moves 6-8" (15-20 cm), replace
RPM sensor.
• If motor unit doesn’t operate, motor unit is overheated. Wait 30 minutes and
retry. If motor unit still will not operate replace logic board.
Symptom: Motor unit doesn’t operate.
• Replace logic board because motor rarely fails.
Motor Circuit Failure. Replace 
Receiver Logic Board.
Motor overheated or possible 
RPM sensor failure. Unplug 
to reset.
Safety reversing sensors
slightly misaligned
(dim or fl ashing LED).
Door control or wire shorted.
Safety reversing sensors 
wire shorted or black/white 
wire reversed.
Safety reversing sensors 
wire open (broken or 
disconnected). 
3 FLASHES
OR
1 FLASH
2 FLASHES
3 FLASHES
6 FLASHES
4 FLASHES
5 FLASHES
Safety Reversing Sensor
Diagnostics
Located On
Motor Unit
LED or 
Diagnostic 
LED
“Learn” 
Button
Installed
Safety Reversing
Sensor
Bell Wire