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If the furnace fails to operate check the following:
• Is the thermostat operating properly?
• Are the blower compartment door(s) in place?
• Is the furnace disconnect closed?
• Has the circuit breaker tripped or the control board fuse
burned open?
• Is the gas turned on?
• Are any manual reset switches open?
• Is the filter dirty or plugged?
• Is the flame sensor coated? (Remove and clean with
steel wool. (Do not use emery cloth or sandpaper!)
• Is there blockage in the condensate drain switch? Also
verify that there is no double trapping of condensate.
• Is the secondary heat exchanger free of debris and
clogs?
• Is evaporator coil clean and free of debris (If applicable).
• Are all the LED's on the furnace control board constantly
ON? If not, refer to
Table 17
Figure 33 (page 39)
to determine fault condition.
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
any component of the furnace must be replaced, use only factory authorized replacement parts specified in the
Replacement Parts List provided online.
Condensate Drain Switch: The Condensate Drain Switch will shut down the furnace if the condensate drain from
the Collector Pan becomes clogged.
Blower Limit Switch: Prevents operation when blower is not operational.
Flame Sensor: 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.
Flame Roll-Out Switch: 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.
Gas Valve: 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.
Inducer Assembly: Vents products of combustion to the outside.
Pressure Switches: 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.
Supply Air Limit Switch: Prevents the air temperature leaving the furnace from exceeding the maximum allowable
outlet air temperature.
TROUBLESHOOTING
or the wiring diagram,
FURNACE COMPONENTS
IMPORTANT NOTE: The furnace will lock out after 5
failed attempts for ignition and will try again every
hour if the call for heat remains.
• If the Inducer Blower is operating, and items above have
been verified, check the Blower Limit Switch and reset
if necessary. See
Figure 43 (page 54)
(page 55)
for component location.
• If the furnace operates when the Blower Limit Switch is
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.
• If the furnace operates when the Flame Rollout Switch
is reset, contact a qualified service technician to identify
and repair the problem.
Diagnostic Description
Control Fault (No Power)
L1/Neutral Polarity Fault
1 Hour Lockout
Normal Operation
Pressure Switch Closed Fault
Pressure Switch Open Fault
Open Limit Switch Fault
Diagnostic Description
Low Flame Sensor Signal
Flame Present
Table 17. Control Board Fault Conditions
Figure 43 (page 54)
or
Figure 44
Green LED
Red LED
Off
Off
Flash
Flash
Alternating Flash
On
On
On
Flash
Flash
On
Flash
Off
Yellow LED
Continuous Flash
On
or
Figure 44 (page
55). If
53
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