GMES8 GCES8 Service Manual

TROUBLESHOOTING
36
PCBBF145(S) CONTROL BOARD
• Turn power OFF
prior to repair.
• Replace pressure
switch with proper
replacement part.
• Normal Operation
• Turn power OFF
prior to repair.
• Replace
integrated
control module
fuse with 3A auto-
motive fuse.
• Read precautions
in “Electrostatic
Discharge” section
of manual.
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.
• Replace or realign igniter.
• Check ame sense signal.
Clean sensor if coated
and/or oxidized.
• Check ue piping for
blockage, proper length,
elbows, and termination.
• Verify proper induced
draft blower performance.
• Turn power
OFF prior to
repair.
• Igniter is frag-
ile, handle with
care.
• Clean ame
sensor.
• See “Vent/Flue
Pipe” section
for piping
details.
• Furnace fails to operate.
• Integrated control mod-
ule diagnostic LED is
ashing ONE (1) ash.
1
1 FLASH
• Failure to establish ame.
Cause may be no gas to
burners, pressure switch
stuck open, bad igniter or
igniter alignment, improper
orices, or coated/oxidized
or improperly connected
ame sensor.
• Loss of ame after estab-
lishment. Cause may be
interrupted gas supply, lazy
burner ames (improper
gas pressure or restriction
in ue and/or combustion
air piping), or improper
induced draft blower perfor-
mance.
• "auxillary limit switch open"-
wired in series with the gas
valve.
• Pressure switch
circuit is closed.
• Induced draft
blower is not
operating.
• Replace induced
draft blower pressure
switch.
• Repair short.
• Furnace fails to operate.
• Integrated control module
diagnostic LED is ashing
TWO (2) ashes.
2
2 FLASHES
• Induced draft blower
pressure switch contacts
sticking.
• Shorts in pressure switch
circuit.
• Inspect pressure
switch hose. Repair, if
necessary,
• Inspect ue for block-
age, proper length, el-
bows, and termination.
Correct as necessary.
• Correct pressure
switch setpoint or
contact motion.
• Tighten or correct
wiring connection.
• Pressure switch hose
blocked, pinched or con-
nected improperly.
• Blocked ue and/or inlet air
pipe, blocked drain system,
or weak induced draft blow-
er.
• Incorrect pressure switch
setpoint or malfunctioning
switch contacts.
• Loose or improperly con-
nected wiring.
• Pressure switch
circuit not closed.
• Induced draft blower
is operating.
• Induced draft blower
runs continuously with
no further furnace opera-
tion.
• Integrated control
module diagnostic LED
is ashing THREE (3)
ashes.
3
3 FLASHES
• Turn power
OFF prior to
repair.
• Replace pres-
sure switch
with proper
replacement
part.
Fault Description(s) Possible Causes
Associated
LED Code
2
• Normal Operation • Normal Operation • None
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.
• 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.
CONTINUOUS
ON