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T
ROUBLESHOOTING
C
HART
54
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 Circulator blower runs continuously. No
furnace operation.
x Integrated control module LED display
provides
E3
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
E3
x Primary limit or
auxiliary limit circuit is
open.
x Rollout limit circuit is
open.
HIGH
LIMIT
OPEN
E3
x Insufficient conditioned air over
the heat exchanger. Blocked
filters, restrictive ductwork,
improper circulator blower speed,
or failed circulator blower motor.
x Flame rollout.
x Misaligned burners, blocked flue
and/or air inlet pipe, or failed
induced draft blower.
x Loose or improperly connected
wiring.
x Check filters and ductwork for
blockage. Clean filters or
remove obstruction.
x Check circulator blower speed
and performance. Correct speed
or replace blower motor if
necessary.
x Check burners for proper
alignment.
x Check flue and air inlet piping
for blockage, proper length,
elbows, and termination. Correct
as necessary.
x Check induced draft blower for
proper performance. Replace if
necessary.
x Tighten or correct wiring
connection.
x Turn power OFF prior to
repair.
x See Specification Sheet
applicable to your model
for allowable rise range
and proper circulator
speed.
x See "Vent/Flue Pipe"
section for piping details.
x Induced draft blower and circulator blower
runs continuously. No furnace operation.
x Integrated control module LED display
provides
E4
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
E4
x Flame sensed with no
call for heat.
IMPROPER
FLAME
E4
x Short to ground in flame sense
circuit.
x Lingering burner flame.
x Slow closing gas valve.
x Correct short at flame sensor or
in flame sensor wiring.
x Check for lingering flame.
x Verify proper operation of gas
valve.
x Turn power OFF prior to
repair.
x No furnace operation.
x Integrated control module LED display
provides
E5
error code.
x ComfortNet™ thermostat displays
“Battery Power”.
E5
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 Normal furnace operation.
x Integrated control module LED display
provides
E6
error code.
E6
x Flame sense micro amp
signal is low
WEAK
FLAME
E6
x Flame sensor is coated/oxidized.
x Flame sensor incorrectly
positioned in burner flame.
x Lazy burner flame due to
improper gas pressure or
combustion air.
x Sand flame sensor if
coated/oxidized.
x Inspect for proper sensor
alignment.
x Check inlet air piping for
blockage, proper length, elbows,
and termination.
x Compare current gas pressure to
rating plate. Adjust as needed.
x Turn power OFF prior to
repair.
x Sand flame sensor with
emery cloth.
x See "Vent/Flue Pipe"
section for piping details.
x See rating plate for proper
gas pressure.
x Furnace fails to operate.
x Integrated control module LED display
provides
E7
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
E7
x Problem with igniter
circuit.
IGNITER
FAULT
E7
x Improperly connected igniter.
x Shorted igniter.
x Poor unit ground.
x Igniter relay fault on integrated
control module.
x Check and correct wiring from
integrated control module to
igniter.
x Replace shorted igniter.
x Check and correct unit ground
wiring.
x Check igniter output from
control. Replace if necessary.
x Turn power OFF prior to
repair.
x Replace igniter with
correct replacement part.
x Replace control with
correct replacement part.