Instruction manual
40
Diagnostic Chart
The red diagnostic LED blinks to assist in troubleshooting the uit. The number of blinks refers to a specific fault code.
Symptoms of
Abnormal
Operation
Associated
LED Code Fault Description Possible Causes Corrective Actions
Notes and
Cautions
■ Furnace fails to
operate.
■ Integrated
control module
diagnostic LED
display
provides no
signal.
None
■ No 115-volt
power to
furnace, or no
24-volt power to
integrated
control module.
■ Blown fuse or
circuit breaker.
■ Internal fault in
Integrated
control module.
■ 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-volt power
to the furnace, and
24-volt power to
integrated control
module
■ Check integrated
control module fuse.
Replace with 3A
automotive fuse, if
necessary.
■ Check for possible
shorts in 115-volt and
24-volt circuits. Repair
as necessary.
■ Replace bad
integrated control
module.
■
Turn off power
prior to repair.
■
Replace
integrated control
module fuse with
3A automotive
fuse.
■
Read precautions
in “Electrostatic
Discharge”
section of manual.
■
Replace
integrated control
module with
current
replacement
parts.
■
LED display is
steady on
Continuous
On
■
Normal
operation
■
Normal operation
■
None
■
Normal operation
■ Furnace fails to
operate.
■ Integrated
control module
diagnostic LED
is flashing
1flash.
1 flash
■ Furnace lockout
due to an
excessive
number of
ignition “retries”
(3 total).
■ Failure to establish
flame. No gas to
burners, front cover
pressure switch stuck
open, bad igniter or
igniter alignment,
improper orifices or
coated/oxidized or
improperly connected
flame sensor.
■ Loss of flame after
establishment.
Interrupted gas supply,
lazy burner flames
(improper gas pressure
or restriction in flue 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. Igniter is fragile,
handle gently.
■
Check flame sense
signal. Sand sensor if
coated and/or oxidized.
■
Check flue piping for
blockage, proper
length, elbows and
termination.
■
Verify proper induced
draft blower
performance.
■ Turn off power
prior to repair.
■ Igniter is fragile,
handle with care.
■ Sand flame
sensor with
emery cloth.
■ See “Vent/Flue
Pipe” section for
piping details.
■ Furnace fails to
operate.
■ Integrated
control module
diagnostic LED
is flashing 2
flashes.
2 flashes
■ Pressure switch
circuit is closed.
■ Induced draft
blower is not
operating.
■ Induced draft blower
pressure switch
contacts sticking.
■ Shorts in pressure
switch circuit.
■ Replace induced draft
blower pressure
switch.
■ Repair short.
■ Turn off power
prior to repair.
■ Replace pressure
switch with
correct
replacement part.
HIGH VOLTAGE!
WARNING
To avoid personal injury or death due to electrical shock, disconnect electrical power
before performing any service or maintenance.