Goodman MH8 Installation Instructions Manual page 38

Symptoms of
Abnormal Operation
• Circulator blower runs
continuously. No furnace
operation.
• Integrated control module
diagnostic LED is flashing
FOUR (4) flashes.
• Induced draft blower and
circulator blower runs
continuously. No furnace
operation.
• Integrated control module
diagnostic LED is flashing
FIVE (5) flashes.
• Furnace fails to operate.
• Integrated control module
diagnostic LED is flashing
SIX (6) flashes.
• No furnace operation.
• Normal furnace
operation.
• Integrated control module
diagnostic LED is
flashing SEVEN (7)
flashes.
2 LED Flash code will cease if power to the control module is interrupted through the disconnect or door switch.
Associated
Fault
Associated
LED Code
2 Description(s)
LED Code 2
• Primary limit
circuit is open.
4
4 FLASHES
• Flame sensed
with no call for
5
heat.
5 FLASHES
• Rollout limit open.
6
• Integrated control
module fuse is
blown.
6 FLASHES
• Flame sense
microamp signal is
7
low.
7 FLASHES
T
ROUBLESHOOTING
Possible Causes
• Insufficient conditioned air
over the heat exchanger.
Blocked filters, restrictive
ductwork, improper
circulator blower speed, or
failed circulator blower.
• Faulty primary limit switch.
• Loose or improperly
connected wiring.
• Short to ground in flame
sense circuit.
• Flame rollout.
• Misaligned burners,
blocked flue and/or air
inlet pipe, or failed
induced draft blower.
• Loose or improperly
connected wiring.
• Short in 24 volt AC
control circuits or safety
circuits.
• Faulty rollout limit.
• Flame sensor is coated/
oxidized.
• Flame sensor incorrectly
positioned in burner
flame.
• Lazy burner flame due to
improper gas pressure or
combustion air.
38
Corrective Action
• Check primary limit.
Replace if necessary.
• Check filters and
ductwork for blockage.
Clean filters or remove
obstruction.
• Check circulator blower
speed and performance.
Correct speed or replace
blower if necessary.
• Tighten or correct wiring
connection.
• Correct short at flame
sensor or in flame
sensor wiring.
• Check burners for proper
alignment.
• Check flue and air inlet
piping for blockage,
proper length, elbows,
and termination. Correct
as necessary.
• Check rollout limit. Replace
if necessary.
• Check induced draft
blower for proper
performance. Replace, if
necessary.
• Tighten or correct wiring
connection.
• Repair short in 24 volt AC
control/safety circuit(s).
• Replace integrated control
module fuse (3A).
• Sand flame sensor.
• Inspect for proper sensor
alignment.
• Compare current gas
pressure to rating plate
info. Adjust as needed.
C
HART
Cautions
& Notes
• Turn power OFF
prior to repair.
• Replace primary
switch with proper
replacement part.
• Replace blower
with correct
replacement part.
• Turn power OFF
prior to repair.
• See "Vent/Flue Pipe"
section for piping
details.
• Replace induced
draft blower with
proper replacement
part.
• Replace integrated
control module fuse
with 3A automotive
fuse.
• Read precautions in
"Electrostatic
Discharge" section
of manual.
• Replace rollout limit
with correct
replacement part.
• Turn power OFF
prior to repair.
• Clean flame sensor
with steel wool.
• See "Vent/Flue
Pipe" section for
piping details.
• See rating plate for
proper gas
pressure.