45
Symptom
LED
Status
Fault Description
Corrective Actions
Normal operation
Normal operation
None
Locate and correct gas interruption
Check front cover pressure switch
operation and verify proper drainage
(hose, wiring, contact operation),
correct if necessary
Replace or realign igniter
Check flame sense signal, clean
sensor if coated or oxidized
Check flue piping for blockage,
proper length, elbows, and
termination
Verify proper induced draft blower
performance
Low stage pressure switch
circuit is closed at start of
heating cycle
Low stage pressure switch
contacts sticking
Short in pressure switch circuit
wiring
Low stage pressure switch
circuit is not closed
Pressure switch hose blocked
pinched, or connected
Inspect flue and/or inlet air piping for
blockage, proper length, elbows,
and termination
Check drain system, correct as
necessary
Check induced draft blower
performance, correct as necessary
Incorrect pressure switch set
point or malfunctioning switch
contacts
Check pressure switch operation,
replace as needed
Loose or improperly connected
wiring
Tighten or correct wiring connection
Primary limit circuit is open
Check filters and ductwork for
blockage Clean filters or remove
obstruction
Insufficient conditioned air over
the heat exchanger
Check circulator blower speed and
performance
Blocked filters, restrictive
ductwork, improper circulator
blower speed, or failed
circulator blower motor
Correct speed or replace blower
motor if necessary
Loose or improperly connected
wiring in high limit circuit
Tighten or correct wiring connection
Flame sensed with no call for
heat
Correct short at flame sensor or in
flame sensor wiring
Short to ground in flame sense
circuit
Lingering burner flame Slow
closing gas valve
Open fuse
Replace fuse
Short in low voltage wiring
Locate and correct short in low
voltage wiring
Flame sense micro amp signal
is minimal
Flame sensor is
coated/oxidized
Flame sensor incorrectly
positioned in burner fame
Check inlet air piping for blockage,
proper length, elbows, and
termination
Compare current gas pressure to
rating plate and adjust as needed
Problem with igniter circuit
Check and correct wiring from
integrated control module to igniter
Improperly connected or
shorted igniter
Poor unit ground
Igniter relay fault on integrated
control module
Check igniter output from control,
replace if necessary
Furnace fails to
operate
Furnace lockout due to an
excessive number of ignition
“retries” (3 total)
Failure to establish flame
Loss of flame after
establishment
Furnace fails to
operate
Replace low stage pressure switch
Repair short in wiring
Normal furnace
operation
Clean flame sensor if coated or
oxidized Inspect for proper flame
sensor alignment
Lazy burner flame due to
improper gas pressure or
combustion air
Induced draft
blower runs
continuously with
no furnace
operation
Inspect pressure switch hose,
repair/replace if necessary
Blocked flue and/or inlet air
pipe, blocked drain system or
weak induced draft blower
Circulator blower
runs continuously
No furnace
operation
Induced draft
blower and
circulator blower
runs continuously
No furnace
operation
Check for lingering or lazy flame
Verify proper operation of gas valve
No furnace
operation
Furnace fails to
operate
Diagnose and replace shorted
igniter as needed Verify and correct
unit ground wiring if needed
Symptom
LED
Status
Fault Description
Corrective Actions
Normal operation
Normal operation
None
High stage pressure switch
circuit is closed at start of
heating cycle.
High stage pressure switch
contacts sticking
Shorts in pressure switch
circuit wiring
Repair short in wiring
Furnace fails to
operate on high
stage; furnace
operates normally
on low stage
Inspect pressure switch hose,
repair/replace if necessary
Inspect flue and/or inlet air piping for
blockage, proper length, elbows,
and termination
Check drain system, correct as
necessary
Check induced draft blower
performance, correct as necessary
Tighten or correct wiring connection
Polarity of 115 volt AC is
reversed
Correct polarity, check and correct
wiring if necessary
Poor unit ground
Verify proper ground, correct if
necessary
Gas valve is not energized
when it should be
Check wiring in gas valve circuit
External Gas Valve Error
Replace integrated control board
Gas valve is energized when it
should not be
Check wiring in gas valve circuit
Internal gas valve error
Replace integrated control board
Furnace fails to
operate.
No 115 power to furnace or no
24 volt power to integrated
control module.
Restore high voltage power to
furnace and integrated control
module.
Blown fuse or tripped circuit
breaker
Correct condition which caused
fuse to open, replace fuse
Integrated control module is
non- functional
Replace non-functional integrated
control module.
Furnace fails to
operate
Grounding fault
Poor neutral connection
Verify neutral wire connection to
furnace & continuity to ground
source
Furnace fails to
operate
Open roll out switch
Check for correct gas pressure
Check for correct burner alignment
Check for and correct burner
restriction
Furnace fails to
operate
Ignitor Open
Check for Ignitor wiring.
Replace Damaged Ignitor
Furnace fails to
operate
Inducer relay Error
Replace integrated control board
Twinning feature
not working
TWIN Error
Check for wiring connections.
Replace integrated control board
Furnace fails to
operate
Internal Faults or IRQ Loss in
Control Board
Replace integrated control board
Furnace fails to
operate on high
stage; furnace
operates normally
on low stage
Induced draft
blower operating
Diagnose and replace high stage
pressure switch if needed
High stage pressure switch
circuit is not closed
Induced draft
blower operating
Furnace fails to
operate
Furnace fails to
operate
Furnace fails to
operate
Integrated control
module LED
display provides
no signal
Troubleshooting Chart
