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T
ROUBLESHOOTING
C
HART
55
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 Furnace fails to operate on high stage;
furnace operates normally on low stage.
x Integrated control module LED display
provides
E8
error code.
E8
x High stage pressure
switch circuit is closed at
start of heating cycle.
x Induced draft blower is
operating.
x Furnace is operating on
low stage only
PS2
CLOSED
E8
x High stage pressure switch
contacts sticking.
x Shorts in pressure switch circuit
wiring.
x Replace high stage pressure
switch.
x Repair short in wiring
x Turn power OFF prior to
repair.
x Replace pressure switch
with correct replacement
part.
x Furnace fails to operate on high stage;
furnace operates normally on low stage.
x Integrated control module LED display
provides
E9
error code.
E9
x High stage pressure
switch circuit is not
closed.
x Induced draft blower is
operating.
x Furnace is operating on
low stage only
PS2 OPEN E9
x Pressure switch hose blocked
pinched, or connected
improperly.
x Blocked flue and/or inlet air pipe,
blocked drain system or weak
induced draft blower.
x Incorrect pressure switch set
point or malfunctioning switch
contacts.
x Loose or improperly connected
wiring.
x Inspect pressure switch hose.
Repair/replace if necessary.
x Inspect flue and/or inlet air
piping for blockage, proper
length, elbows, and termination.
Check drain system. Correct as
necessary.
x Check induced draft blower
performance. Correct as
necessary.
x Correct pressure switch set point
or contact motion.
x Tighten or correct wiring
connection.
x Turn power OFF prior to
repair.
x Replace pressure switch
with correct replacement
part.
x Replace induced draft
blower with correct
replacement part.
x Furnace fails to operate.
x Integrated control module LED display
provides
EA
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
EA
x Polarity of 115 volt AC
is reversed
REVERSED
PLTY
EA
x Polarity of 115 volt AC power to
furnace or integrated module is
revered.
x Poor unit ground
x Review wiring diagram to
correct polarity.
x Verify proper ground. Correct if
necessary.
x Check and correct wiring.
x Turn power OFF prior to
repair.
x Furnace fails to operate.
x Integrated control module LED display
provides d
0
error code.
x ComfortNet™ thermostat “Call for
Service” icon illuminated.
x ComfortNet™ thermostat scrolls “Check
Furnace” message.
d0
x Data not yet on network.
NO NET
DATA
d0
x Furnace does not contain any
shared data.
x Populate shared data set using
memory card.
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.