Service Manual

TROUBLESHOOTING
42
1
Integrated control module will automatically attempt to reset from lockout after one hour.
2
LED Flash code will cease if power to the control module is interrupted through the disconnect or door switch.
• Furnace lockout due
to an excessive
number of ignition
“retries” (3 total)
1
.
• Locate and correct gas
interruption.
• Check front cover
pressure switch
operation (hose, wiring,
contact operation).
Correct if necessary.
• Replace or realign
igniter.
• 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 perfor-
mance.
• Turn power
OFF 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 ONE (1) flash.
1
1 FLASH
• Failure to establish flame.
Cause may be 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. Cause may
be 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.
• Pressure switch
circuit is closed.
• Induced draft
blower is not
operating.
• Replace induced draft
blower pressure
switch.
• Repair short.
• Turn power OFF
prior to repair.
• Replace pressure
switch with proper
replacement part.
• Furnace fails to operate.
• Integrated control module
diagnostic LED is flashing
TWO (2) flashes.
2
2 FLASHES
• Induced draft blower
pressure switch contacts
sticking.
• Shorts in pressure switch
circuit.
• Inspect pressure
switch hose. Repair, if
necessary,
• Inspect flue and/or
inlet air piping for
blockage, proper
length, elbows, and
termination. Check
drain system. Correct
as necessary.
• Correct pressure
switch setpoint or
contact motion.
• Tighten or correct
wiring connection.
• Pressure switch hose
blocked, pinched or
connected improperly.
• Blocked flue and/or inlet air
pipe, blocked drain system,
or weak induced draft
blower.
• Incorrect pressure switch
setpoint or malfunctioning
switch contacts.
• Loose or improperly
connected wiring.
• Pressure switch
circuit not closed.
• Induced draft blower
is operating.
• Induced draft blower
runs continuously with
no further furnace
operation.
• Integrated control
module diagnostic LED
is flashing THREE (3)
flashes.
3
3 FLASHES
• Turn power
OFF prior to
repair.
• Replace
pressure
switch with
proper
replacement
part.
Fault Description(s) Possible Causes
Associated
• Normal Operation • Normal Operation • None
• Normal Operation
ON
CONTINUOUS
ON
• No 115 volt power to
furnace, or no 24
volt power to
integrated control
module.
• Blown fuse or circuit
breaker.
• Integrated control
module has an
internal fault.
• Manual disconnect
switch OFF, door switch
open, or 24 volt wires
improperly connected or
loose.
• Blown fuse or circuit
breaker.
• Integrated control module
has an internal fault.
• Assure 115 and 24 volt
power to furnace
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.
• Furnace fails to operate.
• Integrated control
module diagnostic LED
provides no signal.
NONE
Fault Description(s) Possible Causes Corrective Action
Cautions and
Notes
Symptoms of Abnormal
Operation
Associated
LED Code
2
• LED is Steady On.