TROUBLESHOOTING
18
DM80SN*U
Symptom
LED Status
Fault Description
Corrective Actions
Normal Operation
Stand-by Mode
Normal Operation
None
Furnace fails to operate
Internal Control Fault
Replace control board
Furnace fails to operate
Furnace lockout due to an excessive number of ignition “retries” (3
total)
Failure to establish flame
Loss of flame after establishment
Locate and correct gas interruption
Replace or realign igniter
Check flame sense signal, clean sensor if coated or oxidized
Check flue piping for blockage, proper length, elbows, and
termination
Verify proper induced draft blower performance
Furnace fails to operate
Draft Inducer pressure switch circuit is closed at start of heating cycle
Draft Inducer pressure switch contacts sticking
Short in pressure switch circuit wiring
Replace Draft Inducer pressure switch
Repair short in wiring
Induced draft blower runs
continuously with no
operation
Draft Inducer pressure switch circuit is not closed
Pressure switch hose blocked pinched, or connected improperly
Blocked flue and/or inlet air or weak induced draft blower
Incorrect pressure switch set point or malfunctioning switch contacts
Loose or improperly connected wiring in high limit circuit
Inspect pressure switch hose, repair/replace if necessary
Inspect flue and/or inlet air for blockage, proper length, elbows,
and termination
Check induced draft blower performance, correct as neccesary
Check pressure switch operation, replace as needed
Tighten or correct wiring connection
Circulator blower runs
continuously
No furnace operation
Primary limit circuit is open
Insufficient conditioned air over the heat exchanger
Blocked filters, restrictive ductwork, improper circulator blower speed,
or failed circulator blower motor
Loose or improperly connected wiring in high
limit circuit
Check filters and ductwork for blockage
Clean filters or remove obstruction
Check circulator blower speed and performance
Correct speed or replace blower motor if necessary
Tighten or correct wiring connection
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
Furnace operates but
shows weak flame signal
fault
Flame sense micro amp signal is minimal
Flame sensor is coated/oxidized
Flame sensor incorrectly positioned in burner flame
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 for blockage
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
Summary of Contents for DM80SE
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