Craftsman 139.18473D User's Manual | Page 34

Craftsman Garage Door Opener User's Manual - 139.18473D.
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34

Installed 

Safety Reversing 

Sensor

Safety Sensor

Bell Wire

LED or 
Diagnostic 
LED

"Learn" 
Button  

Diagnostics
Located On 
Motor Unit

Your garage door opener is programmed with 
self-diagnostic capabilities. The “Learn” button/diagnostic
LED will flash 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 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 flashing.
• Realign receiving eye sensor, clean lens and secure brackets. 
• Verify door track is firmly secured to wall and does not move.

Symptom: Motor has overheated; the motor unit does not operate or
trolley is stuck on stop bolt = Motor unit hums briefly; 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 flashing 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 Sensors 
slightly misaligned 
(dim or flashing LED).

Door control or 
wire shorted. 

Safety sensors wire
shorted or black/white
wire reversed. 

Safety sensors wire open
(broken or disconnected). 

1 FLASH

2 FLASHES

3 FLASHES

4 FLASHES

5 FLASHES

6 FLASHES

OR

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