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T
ROUBLESHOOTING
C
HART
56
ComfortNet™
Thermostat Only
Symptoms of Abnormal Operation
(Legacy & ComfortNet™ Thermostat)
Diagnostic/Status
LED Codes
Fault Description
Message Code
Possible Causes Corrective Actions Notes & Cautions
x Operation different than expected or no
operation.
x Integrated control module LED display
provides d
4
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
d4
x Invalid memory card
data.
INVALID
MC DATA
d4
x Shared data set on memory card
has been rejected by integrated
control module
x Verify shared data set is correct
for the specific model. Re-
populate data using correct
memory card if required.
x Turn power OFF prior to
repair
x Use memory card for the
specific model.
x Insert memory card
BEFORE turning power
ON. Memory card may be
removed after data is
loaded.
x Turn power OFF before
removing memory card.
x Error code will be cleared
once data is loaded.
x Furnace fails to operate.
x Integrated control module LED display
provides b
0
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
b0
x Circulator blower motor
is not running when it
should be running.
MOTOR
NOT RUN
b0
x Loose wiring connection at
circulator motor power leads or
circulator motor power leads
disconnected.
x Open circuit in inductor or loose
wiring connection at inductor (3/4
Hp and 1 Hp models only).
x Failed circulator blower motor.
x Tighten or correct wiring
connection.
x Verify continuous circuit
through inductor. Replace if
open or short circuit.
x Check circulator blower motor.
Replace if necessary.
x Turn power OFF prior to
repair
x Replace inductor with
correct replacement part.
x Replace circulator motor
with correct replacement
part.
x Furnace fails to operate.
x Integrated control module LED display
provides b
1
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
b1
x Integrated control
module has lost
communications with
circulator blower motor.
MOTOR
COMM
b1
x Loose wiring connection at
circulator motor control leads.
x Failed circulator blower motor.
x Failed integrated control module.
x Tighten or correct wiring
connection.
x Check circulator blower motor.
Replace if necessary.
x Check integrated control module.
Replace if necessary.
x Turn power OFF prior to
repair
x Replace circulator motor
with correct replacement
part.
x Replace integrated control
module with correct
replacement part.
x Furnace fails to operate.
x Integrated control module LED display
provides b
2
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
b2
x Circulator blower motor
horse power in shared
data set does not match
circulator blower motor
horse power.
MOTOR
MISMATCH
b2
x Incorrect circulator blower motor
in furnace.
x Incorrect shared data set in
integrated control module.
x Verify circulator blower motor
horse power is the same
specified for the specific furnace
model. Replace if necessary.
x Verify shared data set is correct
for the specific model. Re-
populate data using correct
memory card if required.
x Turn power OFF prior to
repair
x Replace motor with correct
replacement part.
x Use memory card for the
specific model
x Insert memory card
BEFORE turning power
ON. Memory card may be
removed after data is
loaded.
x Turn power OFF before
removing memory card.
x Error code will be cleared
once shared data and
motor horse power match.
x Furnace operates at reduced performance.
x Airflow delivered is less than expected.
x Integrated control module LED display
provides b
3
error code.
b3
x Circulator blower motor
is operating in a power,
temperature, or speed
limiting condition.
MOTOR
LIMITS
b3
x Blocked filters.
x Restrictive ductwork.
x Undersized ductwork.
x High ambient temperatures.
x Check filters for blockage.
Clean filters or remove
obstruction.
x Check ductwork for blockage.
Remove obstruction. Verify all
registers are fully open.
x Verify ductwork is appropriately
sized for system. Resize/replace
ductwork if necessary.
x See "Product Description" and
"Location Requirements &
Considerations" for furnace
installation requirements.
x Turn power OFF prior to
repair.