Installation Guide

53
TROUBLESHOOTING
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 43 (page 54) or Figure 44 (page 55). If
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.
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lterdirtyorplugged?
• Istheame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 or the wiring diagram,
Figure 33 (page 39) to determine fault condition.
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) or Figure 44
(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 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
Table17.Control Board Fault Conditions