System Operation - Goodman Amana AMH8 Service Instructions Manual

SYSTEM OPERATION

HEATING - Abnormal Operation
The following presents the probable causes of question-
able furnace operation and how to fix them. Look through
the observation window in the blower access door and
make a note of the number of flashes in sequence be-
tween pauses. Next, refer to the Troubleshooting Chart
on the following pages for an interpretation of the LED
signals and to the information in this section for a de-
scription of the problem.
1. Internal Control Failure with Integrated Ignition
Control. Check for voltage to the furnace . Check
for blown fuse on the control board. If the control
determines it has an internal fault, it enters a locked-
out state. Any of the situations mentioned will cause
the diagnostic LED to provide no signal. The control
board should only be replaced after all other checks
from the Troubleshooting Chart have been verified.
2. System Lockout. If a flame is not sensed during the
first seven (4) seconds after the gas valve is ener-
gized, the control turns off the gas. There will then
be a 30 second delay while the induced draft blower
is energized to purge the heat exchanger. The igni-
tor will next be energized and preheated for (17)
seconds. The gas valve will then be energized. If
flame is not sensed in seven (4) seconds the gas valve
will be de-energized and another purge will occur.
The control will cycle the gas valve a total of three
(3) times before it determines it cannot establish
measurable combustion and enters a locked out
state. The diagnostic light code for this problem is
one short flash followed by a longer pause. The con-
trol can be reset and brought out of lockout mode by
turning the thermostat off for more than (5) seconds
and less than (20) seconds and then back on. It can
also be reset by turning off the electrical disconnect
switch to the furnace for a minimum of 5 seconds.
NOTE: The control board will automatically reset one
hour after lockout occurs. If the furnace frequently has
to be reset, it means that a problem exists that should
be corrected. Refer to Troubleshooting Chart on the fol-
lowing pages for aid in determining the cause.
3. Pressure Switch Stuck Closed. If the control senses
the pressure switch is closed when the induced draft
blower is off, it waits until the fault is corrected.
The diagnostic light code for this problem is two
short flashes followed by a longer pause. The prob-
able cause is either a faulty pressure switch or wir-
ing.
40
4. Pressure Switch Stuck Open. If, after the induced
draft blower is energized, the pressure switch does
not close within 5 minutes, the control will go into
a 1-hour lockout. The control will automatically re-
set from lockout and restart the ignition sequence.
The diagnostic light code for this problem is three
short flashes followed by a pause. The probable
causes are either disconnected hose to the pres-
sure switch, faulty pressure switch or wiring, or
restricted air intake or flue piping.
5. Open Primary or Auxiliary Limit. If the limit con-
trol opens, the air circulator blower will be turned
on until the limit closes. The induced draft blower
will turn off for 5 seconds then turn off. The diag-
nostic light code for this problem is four short
flashes followed by a pause. The probable cause is
either low conditioned air flow due to dirty filter or
resistance in duct work, faulty limit, faulty blower,
or blower speed set to low.
6. Flame Sensed with No Call for Heat. If the control
senses a flame when the gas valve is de-energized,
it will run the air circulation blower and the in-
duced draft blower continuously with no further fur-
nace operation. The diagnostic flash code for this
is a five flashes. The probable causes are either a
short to ground in flame sense circuit, miswiring,
lingering burner flame or a slow closing gas valve.
7. Open Rollout Limit. If the rollout control opens,
the air circulator blower will be energized all the
time. The diagnostic light code for this problem is
six flashes followed by a pause. The probable cause
is either restricted flue piping or improper air re-
quirements. An open fuse will also cause this fault
code.
8. Low Flame Sense Signal. If the furnace continues
to operate and the micro-amp signal from the flame
sensor falls below specified level, the diagnostic
light code for this problem will be seven flashes
followed by a pause. The probable cause is either a
coated/oxidized sensor, incorrectly positioned
senser in burner flame or lazy burner flame due to
improper gas pressure or combustion air.
9. Igniter circuit or poor ground. Improperly con-
nected igniter, bad igniter or poor ground to the
equipment. The diagnostic light code for this prob-
lem is eight flashes.