49
Rev. 2
SYSTEM OPERATION
ABNORMAL OPERATION
(Models with Heatcraft HSI-2 Integrated Ignition Control)
The following presents the probable causes of questionable
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 between pauses.
Next, refer to the
DIAGNOSTIC SIGNAL CHART for an in-
terpretation of the signals and to this section for a descrip-
tion.
1. Internal Control Failure with Integrated Ignition
Control. If the control determines it has an internal fault,
it enters a locked-out state, and the diagnostic light will
light continuously with no flashes. The control should
be replaced.
2. System Lockout. If a flame is not sensed during the
first seven (7) seconds after the gas valve is energized,
the control turns off the gas. There will then be a 60
second delay while the induced draft blower is energized
to purge the heat exchanger. The ignitor will next be
energized and preheated for 27 seconds. The gas valve
will then be energized. If flame is not sensed in seven (7)
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. If flame is sensed but lost after ten (10) sec-
onds, the control will recycle this series of three tries
four (4) more times before locking out. The diagnostic
light code for this problem is one short flash followed
by a longer pause. The control can be reset and brought
out of lockout mode by turning the thermostat off and
then back on. It can also be reset by turning off the elec-
trical disconnect switch to the furnace for 30 seconds.
Note: The control board will automatically reset one hour
after lockout occurs. If the furnace frequently has to be re-
set, it means that a problem exists that should be corrected.
Refer to
TROUBLESHOOTING - DIAGNOSTIC CHART on
the following 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 di-
agnostic light code for this problem is two short flashes
followed by a longer pause. The probable cause is either
a faulty pressure switch or wiring.
4. Pressure Switch Stuck Open. If, after the induced draft
blower is energized, the pressure switch does not close,
the control will keep the induced draft blower on and wait
for the switch to close. The diagnostic light code for this
problem is three short flashes followed by a pause.
The probable causes are either disconnected hose to
the pressure switch, faulty pressure switch or wiring, or
restricted air intake or flue piping.
5. Open Primary or Auxiliary Limit. If the limit control
opens, the air circulation and induced draft blower will
be turned on until the limit closes. The diagnostic 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. Open Rollout Limit. If the rollout control opens, the air
circulation blower and induced draft blower will be ener-
gized all the time. The diagnostic light code for this prob-
lem is five flashes followed by a pause. The probable
cause is either restricted flue piping or improper air re-
quirements.
7. Reversed Polarity. If the 115V or 24V AC power leads
are reversed, the furnace will fail to operate. The diag-
nostic light code for this problem is six flashes followed
by a pause. The probable cause is either the 115V AC
power to furnace or integrated control module is reversed,
the 24V AC orange and gray wires to transformer are
reversed, or poor unit ground.
8. Pressure Switch Opened Five Times During A
Single Call for Heat. If the furnace fails to operate due
to pressure switch opening five times during a single call
for heat. The diagnostic light code for this problem is
eight flashes followed by a pause. The probable cause
is either the pressure switch hose is blocked, pinched,
or misconnected, blocked flue or drain system, weak
induced draft blower, incorrect pressure switch set point
or faulty pressure switch, or loose or misconnected wir-
ing.
Note: There is a twenty minute lockout if the pressure switch
has tripped five times during a single call for heat.
9. Primary or Auxiliary Limit Opened Five Times Dur-
ing a Single Call for Heat. If the furnace fails to oper-
ate due to primary or auxiliary limit opening five times
during a single call for heat, the control will run the air
circulation blower continuously with no further furnace
operation. The diagnostic light code for this problem is
nine flashes followed by a pause. The probable cause
is either low conditioned air flow due to dirty filter(s) or
resistance in duct work, faulty limit, faulty blower, or blower
speed set to low.
Note: There is a one hour lockout if either the primary or
auxiliary limit has tripped five times during a single call for
heat.
10. 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 induced draft
blower continuously with no further furnace operation.
The diagnostic flash code for this is a continuous flash.
The probable cause is either a short to ground in flame
sense circuit or miswiring.
