Concord
Concord Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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1 FLASH
Furnace will not start; status LED shows 1 flash repeating, inducer and blower are off.
Ignition Failure Lockout
10 FLASHES
Furnace shuts down; status LED shows 10 flashes repeating; blower may run.
Flame Rollout or Manual Reset Limit Open
11 FLASHES
Furnace does not respond to thermostat; status LED shows 11 flashes repeating.
Limit Switch Circuit Lockout
2 FLASHES
Furnace attempts to start but shuts down quickly; status LED shows 2 flashes repeating.
Pressure Switch Stuck Closed
3 FLASHES
Furnace will not ignite; inducer runs but burners never light; status LED shows 3 flashes repeating.
Pressure Switch Stuck Open
4 FLASHES
Burners ignite but shut off quickly; status LED shows 4 flashes repeating.
Open High Limit Switch
5 FLASHES
Furnace locks out; burners do not light; status LED shows 5 flashes repeating.
Flame Sensed With Gas Valve Off
6 FLASHES
Furnace will not start; status LED shows 6 flashes repeating; blower may run continuously.
Pressure Switch Cycle Lockout
7 FLASHES
Furnace will not run; status LED shows 7 flashes repeating; blower may run on low speed.
Flame Sense Lost During Run
8 FLASHES
Furnace does not start; status LED shows 8 flashes repeating.
Low Flame Sense Signal
9 FLASHES
Furnace will not operate; status LED shows 9 flashes repeating.
Line Voltage Polarity or Ground Fault
HARD LOCKOUT
Furnace LED indicates hard lockout (often rapid flashing or specific pattern); furnace will not attempt ignition until power is cycled.
Ignition Retry Limit Exceeded
NO LED
Concord furnace has no LED lights and does not respond; blower and inducer are off.
No Power to Furnace
STEADY ON
Status LED on Concord furnace is solid ON with no flashing; furnace may or may not operate.
Normal Operation or Idle (No Fault)
Symptom
Blower motor hums but does not start, or starts slowly and overheats.
Blower Motor or Capacitor Failure
Symptom
Furnace blower runs continuously even when thermostat is not calling for heat or fan.
Blower Stuck On
Symptom
Furnace cycles on and off frequently (short cycles) and the house temperature fluctuates.
Short Cycling Due to Control or Sizing Issues
Symptom
Furnace emits a strong chemical or burning plastic odor during operation.
Overheating Electrical or Plastic Components
Symptom
Furnace ignites but produces yellow, lazy flames instead of sharp blue flames.
Improper Combustion
Symptom
Furnace inducer motor is very loud, squealing, or grinding during operation.
Inducer Motor Bearing Failure
Symptom
Furnace is very loud outside at the vent termination (high-efficiency models), with whistling or roaring noise.
Vent Airflow Noise
Symptom
Furnace is very noisy during operation with rattling or vibrating sounds from the cabinet.
Cabinet Vibration and Loose Components
Symptom
Furnace makes loud banging or booming noise at startup when burners ignite.
Delayed Ignition
Symptom
Furnace occasionally makes a high-pitched whine during operation.
Airflow or Motor Noise
Symptom
Furnace occasionally trips the household circuit breaker.
Overcurrent or Short Circuit
Symptom
Furnace produces a burning dust smell at the beginning of the heating season.
Dust Burn-Off on Heat Exchanger
Symptom
Furnace runs but does not produce warm air; blower is on, air from registers is cool or only slightly warm.
Burners Not Igniting or Short Cycling
Symptom
Furnace runs but gas bill is unusually high and runtime seems excessive.
Low Efficiency Operation
Symptom
Furnace runs but shuts off after a few minutes, then restarts; home never reaches set temperature.
High Limit Short Cycling
Symptom
Furnace runs but some rooms are too cold while others are too warm.
Air Distribution Imbalance
Symptom
Furnace starts but shuts down immediately when the blower door is installed; runs with door removed (defeating switch).
Door Switch or Airflow Restriction Issue
Symptom
Furnace starts normally but shuts down when the blower comes on.
Flame Disturbance or Pressure Switch Opening on Blower Start
Symptom
Furnace will not start at all; thermostat appears to be working but there is no response from the furnace.
No Call for Heat Reaching Furnace
Symptom
Thermostat goes blank when furnace starts, then comes back on after a while.
Low-Voltage Power Drop or Short
Symptom
Water is dripping from the metal flue pipe of a standard-efficiency Concord furnace.
Flue Condensation
Symptom
Water is leaking around the base of a high-efficiency (PVC vented) Concord furnace.
Condensate Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 1 FLASH |
Furnace will not start; status LED shows 1 flash repeating, inducer and blower are off.
|
Ignition Failure Lockout | View Details |
| 10 FLASHES |
Furnace shuts down; status LED shows 10 flashes repeating; blower may run.
|
Flame Rollout or Manual Reset Limit Open | View Details |
| 11 FLASHES |
Furnace does not respond to thermostat; status LED shows 11 flashes repeating.
|
Limit Switch Circuit Lockout | View Details |
| 2 FLASHES |
Furnace attempts to start but shuts down quickly; status LED shows 2 flashes repeating.
|
Pressure Switch Stuck Closed | View Details |
| 3 FLASHES |
Furnace will not ignite; inducer runs but burners never light; status LED shows 3 flashes repeating.
|
Pressure Switch Stuck Open | View Details |
| 4 FLASHES |
Burners ignite but shut off quickly; status LED shows 4 flashes repeating.
|
Open High Limit Switch | View Details |
| 5 FLASHES |
Furnace locks out; burners do not light; status LED shows 5 flashes repeating.
|
Flame Sensed With Gas Valve Off | View Details |
| 6 FLASHES |
Furnace will not start; status LED shows 6 flashes repeating; blower may run continuously.
|
Pressure Switch Cycle Lockout | View Details |
| 7 FLASHES |
Furnace will not run; status LED shows 7 flashes repeating; blower may run on low speed.
|
Flame Sense Lost During Run | View Details |
| 8 FLASHES |
Furnace does not start; status LED shows 8 flashes repeating.
|
Low Flame Sense Signal | View Details |
| 9 FLASHES |
Furnace will not operate; status LED shows 9 flashes repeating.
|
Line Voltage Polarity or Ground Fault | View Details |
| HARD LOCKOUT |
Furnace LED indicates hard lockout (often rapid flashing or specific pattern); furnace will not attempt ignition until power is cycled.
|
Ignition Retry Limit Exceeded | View Details |
| NO LED |
Concord furnace has no LED lights and does not respond; blower and inducer are off.
|
No Power to Furnace | View Details |
| STEADY ON |
Status LED on Concord furnace is solid ON with no flashing; furnace may or may not operate.
|
Normal Operation or Idle (No Fault) | View Details |
| – |
Blower motor hums but does not start, or starts slowly and overheats.
|
Blower Motor or Capacitor Failure | View Details |
| – |
Furnace blower runs continuously even when thermostat is not calling for heat or fan.
|
Blower Stuck On | View Details |
| – |
Furnace cycles on and off frequently (short cycles) and the house temperature fluctuates.
|
Short Cycling Due to Control or Sizing Issues | View Details |
| – |
Furnace emits a strong chemical or burning plastic odor during operation.
|
Overheating Electrical or Plastic Components | View Details |
| – |
Furnace ignites but produces yellow, lazy flames instead of sharp blue flames.
|
Improper Combustion | View Details |
| – |
Furnace inducer motor is very loud, squealing, or grinding during operation.
|
Inducer Motor Bearing Failure | View Details |
| – |
Furnace is very loud outside at the vent termination (high-efficiency models), with whistling or roaring noise.
|
Vent Airflow Noise | View Details |
| – |
Furnace is very noisy during operation with rattling or vibrating sounds from the cabinet.
|
Cabinet Vibration and Loose Components | View Details |
| – |
Furnace makes loud banging or booming noise at startup when burners ignite.
|
Delayed Ignition | View Details |
| – |
Furnace occasionally makes a high-pitched whine during operation.
|
Airflow or Motor Noise | View Details |
| – |
Furnace occasionally trips the household circuit breaker.
|
Overcurrent or Short Circuit | View Details |
| – |
Furnace produces a burning dust smell at the beginning of the heating season.
|
Dust Burn-Off on Heat Exchanger | View Details |
| – |
Furnace runs but does not produce warm air; blower is on, air from registers is cool or only slightly warm.
|
Burners Not Igniting or Short Cycling | View Details |
| – |
Furnace runs but gas bill is unusually high and runtime seems excessive.
|
Low Efficiency Operation | View Details |
| – |
Furnace runs but shuts off after a few minutes, then restarts; home never reaches set temperature.
|
High Limit Short Cycling | View Details |
| – |
Furnace runs but some rooms are too cold while others are too warm.
|
Air Distribution Imbalance | View Details |
| – |
Furnace starts but shuts down immediately when the blower door is installed; runs with door removed (defeating switch).
|
Door Switch or Airflow Restriction Issue | View Details |
| – |
Furnace starts normally but shuts down when the blower comes on.
|
Flame Disturbance or Pressure Switch Opening on Blower Start | View Details |
| – |
Furnace will not start at all; thermostat appears to be working but there is no response from the furnace.
|
No Call for Heat Reaching Furnace | View Details |
| – |
Thermostat goes blank when furnace starts, then comes back on after a while.
|
Low-Voltage Power Drop or Short | View Details |
| – |
Water is dripping from the metal flue pipe of a standard-efficiency Concord furnace.
|
Flue Condensation | View Details |
| – |
Water is leaking around the base of a high-efficiency (PVC vented) Concord furnace.
|
Condensate Leak | View Details |
No matching codes found
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