14
TROUBLESHOOTING INFORMATION: UNITARY DIAGNOSTIC CODES
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 LED display is ON continuously ON
x Normal operation None None
x Normal operation x None x Normal operation
x Electric heaters fail to energize on a call for
W1 or Auxiliary/Emergency heat
x Integrated control module LED display
provides the indicated error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated
x ComfortNet™ thermostat scrolls “Check
Air Handler” message
1 Flash x Heater kit selected via
dipswitches is too large
for heater kits specified
in shared data set
HTR TOO
LARGE
Ec x Heater kit selected via
dipswitches is too large for heater
kits in shared data set
x Verify electric heat dipswitch
settings
x Verify the installed electric
heater is valid for the modular
blower. Check nameplate or
Specification Sheet applicable to
your model* for allowable heater
kit(s).
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 Electric heat airflow is higher than
expected on a call for W1 or
Auxiliary/Emergency heat
x Integrated control module LED display
provides the indicated error code.
1 Flash x Heater kit selected via
dipswitches is too small
for heater kits specified
in shared data set
HTR TOO
SMALL
Ec x Heater kit selected via
dipswitches is too small for heater
kits in shared data set
x Verify electric heat dipswitch
settings
x Verify the installed electric
heater is valid for the modular
blower. Check nameplate or
Specification Sheet applicable to
your model* for allowable heater
kit(s).
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 Electric heat airflow is higher than
expected on a call for W1 or
Auxiliary/Emergency heat
x Integrated control module LED display
provides the indicated error code.
1 Flash x Heater kit selected via
dipswitches does not
heater kits specified in
shared data set
NO HTR
MATCH
Ec x Heater kit selected via
dipswitches is doesn’t match
heater kits in shared data set
x Verify electric heat dipswitch
settings
x Verify the installed electric
heater is valid for the modular
blower. Check nameplate or
Specification Sheet applicable to
your model* for allowable heater
kit(s).
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 No modular blower operation.
x Integrated control module LED display
provides the indicated error code.
x ComfortNet™ thermostat displays “Battery
Power”
5 Flashes x Open Fuse Not
Displayed
Not
Displayed
x Short in low voltage wiring x Locate and correct short in low
voltage wiring
x Turn power OFF prior to
repair.
x Replace fuse with 3-amp
automotive type
x Modular blower fails to operate
x Integrated control module LED display
provides no signal.
x ComfortNet™ thermostat “Call for
Service” icon illuminated
x ComfortNet™ thermostat scrolls “Check
Air Handler” message
None x No 208/230 volt power
to modular blower or no
24 volt power to
integrated control
module
x Blown fuse or circuit
breaker
x Integrated control
module has an internal
fault.
INTERNAL
FAULT
EE x Manual disconnect switch OFF or
24 volt wire improperly
connected or loose
x Blown fuse or circuit breaker
x Integrated control module has an
internal fault
x Assure 208/230 volt and 24 volt
power to modular blower and
integrated control module.
x Check integrated control module
fuse (3A). Replace if necessary.
x Check for possible shorts in
208/230 volt and 24 volt circuits.
Repair as necessary.
x Replace bad integrated control
module.
x Turn power OFF prior to
repair.
x Replace integrated control
module fuse with 3A
automotive fuse.
x Replace integrated control
module with correct
replacement part
x Read precautions in
“Electrostatic Discharge”
section of manual.