55
TROUBLESHOOTING
• Isthethermostatoperatingproperly?
• Aretheblowercompartmentdoor(s)inplace?
• Isthefurnacedisconnectclosed?
• Has the circuit breaker tripped or the control board
fuseburnedopen?
• Isthegasturnedon?
• Areanymanualresetswitchesopen?
• Isthelterdirtyorplugged?
• Istheamesensorcoated?(Removeandcleanwith
steel wool.
• Isthereblockageinthecondensatedrainswitch?Also
verify that there is no double trapping of condensate.
• Is the secondary heat exchangerfree of debris and
clogs?
• Isevaporatorcoilcleanandfreeofdebris(Ifapplicable).
• Are all the LED’s on the furnace control board
constantlyON? If not, referto Table 18 or the wiring
diagram, Figure 33 (page 40) & Figure 34 (page 41)
to determine fault condition.
• ArealltheLED’sonthemotorcontrolboardconstantly
ON?Ifnot,refertoTable 19 to determine fault condition.
IMPORTANT NOTE:
• If the Inducer Blower is operating, and items above
have been verified, check the Blower Limit Switch and
reset if necessary. See Figure 44 (page 56) or Figure
45 (page 57)
for component location.
• IfthefurnaceoperateswhentheBlowerLimitSwitchis
reset, contact a qualified service technician to identify
and repair the problem.
• If the furnace still doesn’t operate, check the Flame
Roll-out Switches and reset if necessary.
• IfthefurnaceoperateswhentheFlameRolloutSwitch
is reset, contact a qualified service technician to
identify and repair the problem.
DIAGNOSTIC DESCRIPTION GREEN LED RED LED
Control Fault (No Power) Off Off
L1/Neutral Polarity Fault Flash Flash
1 Hour Lockout Alternating Flash
Normal Operation On On
Pressure Switch Closed Fault On Flash
Pressure Switch Open Fault Flash On
Open Limit Switch Fault Flash Off
DIAGNOSTIC DESCRIPTION YELLOW LED
Low Flame Sensor Signal Continuous Flash
Flame Present On
Control Board Fault Conditions
DIAGNOSTIC DESCRIPTION RED LED GREEN LED
Control Fault (No Power) Off Off
Normal Operation On On
Motor Fault On Flash
Twin Fault (No Motor Fault) Flash On
Communications Fault Flash Flash
Motor Control Board Fault Conditions
FURNACE COMPONENTS
The descriptions below are various functional components
that affect the operation and shutting down of this furnace.
Some of these components and their locations are shown
in Figure 44 (page 56) or Figure 45 (page 57). If any
component of the furnace must be replaced, use only
factory authorized replacement parts specified in the
Replacement Parts List provided online.
The Condensate Drain Switch
will shut down the furnace if the condensate drain from
the Collector Pan becomes clogged.
Prevents operation when blower
is not operational.
Verifies when a flame has carried over
from the igniter to the opposite end burner. If no flame
is detected, the furnace will shut down within 4 seconds.
Verifies that the burner flames
are drawn into the heat exchanger tubes. If the burner
flames are not properly drawn into the heat exchanger, the
flame roll-out switch will close the gas valve and initiate
the shutdown cycle.
Controls the flow of gas to the burners. When
the gas valve is energized it automatically opens and
regulates the gas pressure in the manifold.
Vents products of combustion to
the outside.
Verifies that the inducer is drawing
the combustion gases through the heat exchanger. The
pressure switch prevents furnace operation with excessive
flue/condensate blockage or improper inducer operation.
Prevents the air temperature
leaving the furnace from exceeding the maximum allowable
outlet air temperature.
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