48
T
ROUBLESHOOTING
C
HART
Symptoms of Abnormal
Operation (Legacy &
ComfortNet™ Thermostat)
Diagnostic/
Status LED
Codes
Fault Description
ComfortNet™
Thermostat Only
Possible Causes
Corrective Actions
Notes & Cautions
Message
Code
• Furnace fails to operate
• Integrated control module
LED display provides no
signal.
• ComfortNet™ thermostat
“Call for Service” icon
illuminated
• ComfortNet™ thermostat
scrolls “Check Furnace”
message
None
• No 115 power to
furnace or no 24 volt
power to integrated
control module
• Blown fuse or circuit
breaker
• Integrated control
module has an
internal fault
INTERNAL
FAULT
EE
• Manual disconnect switch
OFF, door switch open or
24 volt wire improperly
connected or loose
• Blown fuse or circuit
breaker
• Integrated control module
has an internal fault
• Assure 115 and 24
volt power to furnace
and integrated control
module.
• Check integrated control
module fuse (3A).
Replace if necessary.
• Check for possible
shorts in 115 and 24
volt circuits. Repair as
necessary.
• Replace bad integrated
control module.
• Turn power OFF prior
to repair.
• Replace integrated
control module fuse
with 3A automotive
fuse.
• Read precautions
in “Electrostatic
Discharge” section of
manual.
• Replace control with
correct replacement
part
• LED display indicates On
On
• Normal operation
None
None
• Normal operation
• None
• Normal operation
• Furnace fails to operate
• Integrated control module
LED display provides E0
error code.
• ComfortNet™ thermostat
“Call for Service” icon
illuminated.
• ComfortNet™ thermostat
scrolls “Check Furnace”
message.
E0
• Furnace lockout
due to an excessive
number of ignition
“retries” (3 total)
LOCKOUT
E0
• Failure to establish fame.
Cause may be no gas
to burners, front cover
pressure switch stuck
open, bad igniter or igniter
alignment, improper
orifces, or coated/oxidized
or improperly connected
fame sensor.
• Loss of fame after
establishment. Cause
may be interrupted gas
supply, lazy burner fames
(improper gas pressure
or restriction in fue and/
or combustion air piping),
front cover pressure switch
opening, or improper
induced draft blower
performance.
• Locate and correct gas
interruption.
• Check front cover
pressure switch operation
(hose, wiring, contact
operation). Correct if
necessary.
• Replace or realign igniter.
• Check fame sense
signal. Sand sensor if
coated and/or oxidized.
• Check fue piping for
blockage, proper length,
elbows, and termination.
• Verify proper induced
draft blower performance.
• Turn power OFF prior
to repair.
• Igniter is fragile,
handle with care.
• Sand fame sensor
with emery cloth.
• See “Vent/Flue Pipe”
section for piping
details.
• Furnace fails to operate.
• Integrated control module
LED display provides E1
error code.
• ComfortNet™ thermostat
“Call for Service” icon
illuminated.
• ComfortNet™ thermostat
scrolls “Check Furnace”
message.
E1
• Low stage pressure
switch circuit is
closed at start of
heating cycle.
PS1
CLOSED
E1
• Low stage pressure switch
contacts sticking.
• Shorts in pressure switch
circuit wiring.
• Replace low stage
pressure switch.
• Repair short in wiring.
• Turn power OFF prior
to repair.
• Replace pressure
switch with proper
replacement part.
