Chamberlain Merlin Whisper Drive MT3850 Installation And Operating Instructions Manual page 27

TROUBLE SHOOTING (ONBOARD DIAGNOSTICS)
Your opener is equipped with a self diagnostic
program which can provide trouble status through
as series of flashes of the Indicator Light under the
Lens Cover.
1 Flash: Safety reversing sensors wire open (broken
or disconnected).
OR
2 Flashes: Safety reversing sensors wire shorted or
black/white wire reversed.
Symptom: One or both of the Indicator lights on the
safety reversing sensors do not glow steadily.
• 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 opener.
• Remove sensors from brackets and shorten sensor
wires to 300-600mm from the back of each sensor.
• Re-attach sending eye to opener 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 reversing sensors.
3 Flashes: Control console or wire shorted.
Symptom: No LCD Display.
• Inspect control console/wires for a short (staple in wire.
Replace as needed).
• Disconnect wires at control console and touch wires
together. If opener activates, replace control console.
• If opener does not activate, disconnect control console
wires from opener. Momentarily short across red and
white terminals with jumper wire. If opener activates,
replace control console wires.
4 Flashes: Safety reversing sensors slightly
Symptom: Sending indicator light glows steadily,
• Realign receiving eye sensor, clean lens and secure
• Verify door track is firmly secured to wall and does not
Indicator Light
5 Flashes: Possible RPM sensor failure. Unplug to
Black Button
Orange Button
Symptom: RPM Sensor = Short travel 150-200mm.
• Unplug opener to reset. Try to operate opener, check
• If it is still flashing 5 times and opener moves 150-
26
misaligned (dim or flashing LED).
receiving indicator light is
dim or flashing.
brackets.
move.
reset.
diagnostic code.
200mm, a service will be required.