Chamberlain JDC Manual page 61

Troubleshooting (continued)
Display
Code
Message
F102 F102 BBU
DISCONN
F105 F105 AC
FAIL
F106 F106 WC
SHORT
F120 F120 MAINT
DUE
F121 F121 OVER
CYCLED
Possible
Description
Causes
Battery is Backup battery
learned to the is disconnected
system but
the battery is
not detected
Battery is worn
out or has failed
Battery fuses
blown
AC failure. Power outage
System is
running on
battery.
Input voltage
outside
specifications
Indicates wall Wall control is
control is intentionally
removed and disconnected
jumpered out.
Wiring short
circuit
Damaged wall
control
Maintenance Maintenance
counter counter
reached reached preset
preset limit limit
Standard/ Operator has
extended been cycled too
cycle count many times in a
reached short period of
time
Diagnosis
Verify all battery wiring is
connected securely and
properly to the correct
terminals and with the
correct polarity.
Batteries can be tested
with a suitable battery
tester.
Older batteries are more
likely to be worn out, as
are batteries that are
used often.
Visually inspect battery
fuses or measure the
fuses with a multimeter
for continuity.
Check for proper voltage
at the input of the
operator
Check for proper voltage
at the input of the
operator
Error message is
informational only.
Inspect wiring for short
circuits, damage, etc.
Replace wall control with
known-good unit, then
power cycle the operator
F120 error code
Refer to specified cycle
ratings for the operator
model that is installed
61
Resolution
Correct any wiring issues.
Replace batteries.
Always replace both batteries
as a set. Do not mix old and new
batteries or use mismatched
types.
If fuses are blown, replace both
together with new fuses.
Error code will resolve when
power is restored
Ensure voltage supplied to the
operator is within the specified
operating range
Liftmaster strongly recommends
using the provided LCD wall
control with the operator.
Resolve any faults found, then
power cycle the operator
If known good wall control
resolves the issue, replace the
bad wall control
Reset maintenance counter
using the menu through the wall
control
Reduce cycle rate to ensure it
is within specifications for the
operator