TROUBLESHOOTING
37
Symptom
LED Status
Fault Description
Corrective Actions
Induced draft blower and
circulator blower runs
continuously
No furnace operation
Flame sensed with no call for
heat
Short to ground in flame sense
circuit
Lingering burner flame
Slow closing gas valve
Correct short at flame sensor or in flame sensor
wiring
Check for lingering or lazy flame
Verify proper operation of gas valve
No furnace operation
Open fuse
Short in low voltage wiring
Replace fuse
Locate and correct short in low voltage wiring
Normal furnace operation
Flame sense micro amp signal is
low
Flame sensor is coated/oxidized
Flame sensor incorrectly
positioned in burner fame
Lazy burner flame due to
improper gas pressure or
combustion air
Clean flame sensor if coated or oxidized
Inspect for proper flame sensor alignment
Check inlet air piping for blockage, proper length,
elbows, and termination
Compare current gas pressure to rating plate and
adjust as needed
Furnace fails to operate
Problem with igniter circuit
Improperly connected or shorted
igniter
Poor unit ground
Igniter relay fault on integrated
control module
Check and correct wiring from integrated control
module to igniter
Diagnose and replace shorted igniter as needed
Verify and correct unit ground wiring if needed
Check igniter output from control, replace if
necessary
Furnace fails to operate on
high stage; furnace operates
normally on low stage
Induced draft blower
operating
High stage pressure switch
circuit is closed at start of
heating cycle.
High stage pressure switch
contacts sticking
Shorts in pressure switch circuit
wiring
Diagnose and replace high stage pressure switch if
needed
Repair short in wiring
Furnace fails to operate on
high stage; furnace operates
normally on low stage
Induced draft blower
operating
High stage pressure switch
circuit is not closed
Furnace is operating on low
stage only
Inspect pressure switch hose, repair/replace if
necessary
Inspect flue and/or inlet air piping for blockage,
proper length, elbows, and termination
Check drain system, correct as necessary
Check induced draft blower performance, correct
as necessary
Tighten or correct wiring connection
Furnace fails to operate
A
Polarity of 115 volt AC is
reversed
Poor unit ground
Correct polarity, check and correct wiring if
necessary
Verify proper ground, correct if necessary
Furnace fails to operate
Gas valve is not energized when
it should be
External Gas Valve Error
Check wiring in gas valve circuit
Replace integrated control board
Furnace fails to operate
C
Gas valve is energized when it
should not be
Internal gas valve error
Check wiring in gas valve circuit
Replace integrated control board
