American Standard Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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01
The furnace control board shows error code 01, and the unit will not start a heating cycle.
Ignition Lockout Due to Recycles Exceeded
02
Error code 02 is displayed, and the furnace inducer motor does not start; there is no ignition sequence.
Pressure Switch Stuck Closed
03
Error code 03 is displayed, and the inducer runs continuously, but the burners will not light.
Pressure Switch Stuck Open
04
Error code 04 is displayed, and the furnace cycles the inducer and igniter, but the gas valve never opens.
Open High Limit Switch
05
Error code 05 is displayed, and the furnace starts then shuts down after a few seconds of flame.
Flame Sensed But Lost During Run
06
Error code 06 is displayed, and the furnace blower runs, but the burners will not ignite.
Rollout Switch Open
07
Error code 07 is displayed, and the furnace will not respond to the thermostat; there is no inducer or blower operation.
Low Voltage Lockout / No 24V from Transformer
08
Error code 08 is displayed, and the indoor blower runs continuously, but no heat call is recognized.
Stuck Fan Relay or Fan On After Power Up
09
Error code 09 is displayed, and the furnace attempts to start but shuts down with the blower running for cool-down.
Secondary Limit or Auxiliary Limit Open
10
Error code 10: Furnace cycles on and off rapidly without reaching the set temperature.
Flame Sense Microampere Out of Range / Nuisance Flame Loss
11
Error code 11: Furnace does not respond to the thermostat; LED indicates an internal control fault.
Internal Control Board Failure
12
Error code 12: Furnace starts but shuts down with the inducer and blower running, and no flame is established.
Ignition Failure / No Flame Detected
13
Error code 13: Furnace locks out after several failed ignition attempts, requiring a power reset.
Ignition Lockout – Repeated Flame Failure
14
Error code 14: Furnace shuts down due to high temperature; the blower runs for an extended cool-down period.
Primary Limit Open – Overheat Condition
15
Error code 15: Furnace does not start; LED indicates improper line voltage or polarity.
Line Voltage Polarity / Ground Fault
16
Error code 16: Furnace intermittently shuts down; the board indicates flame sensed when there is no call for heat.
False Flame Sense / Flame Signal Present with Gas Off
17
Error code 17: Furnace runs the inducer but never proceeds to ignition; the pressure switch error persists.
Pressure Switch Did Not Open After Cycle
18
Error code 18: Furnace shuts down with water present in the cabinet or around the base.
Condensate Overflow / Drain Blocked
19
Error code 19: Furnace fan runs but there is no heat; the thermostat appears to be calling.
Communication Error with Communicating Thermostat
20
Error code 20, and the furnace will not start. The LED indicates a lockout due to too many retries.
Hard Lockout – Exceeded Retry Limit
Symptom
Furnace runs but the carbon monoxide detector alarms or occupants experience headaches.
Combustion / Venting Safety Issue
Symptom
Furnace starts and stops with a loud whooshing or rumbling sound in the vent pipes.
Vent Airflow / Resonance Problem
Symptom
Furnace vibrates excessively and rattles ductwork when running.
Mechanical Vibration / Imbalanced Blower
Symptom
Strong burning or electrical smell when the furnace runs.
Overheating Components or Dust Burn-Off
Symptom
The furnace blower starts but stops after a few seconds, then tries again repeatedly.
Blower Motor Overload or Control Issue
Symptom
The furnace burners light but shut off after 3–10 seconds, repeating several times.
Flame Sensor Not Proving Flame
Symptom
The furnace frequently trips the household circuit breaker.
Electrical Overload or Short Circuit
Symptom
The furnace makes a loud banging or booming noise at startup.
Delayed Ignition / Burner Light-Off Problem
Symptom
The furnace produces a high-pitched whine or squeal during operation.
Blower or Inducer Motor Bearing Wear
Symptom
The furnace runs but some rooms are too hot while others are too cold.
Airflow Imbalance / Duct Issues
Symptom
The furnace runs, but the house never reaches the set temperature, and the supply air feels lukewarm.
Underfiring or Low Heat Output
Symptom
The furnace short cycles, turning on and off frequently without long run times.
Short Cycling Due to Overheat or Oversizing
Symptom
The furnace will not start at all; there are no lights on the control board, and no blower or inducer operation.
No Power to Furnace
Symptom
The indoor blower runs continuously even when the thermostat is not calling for heat or fan.
Blower Stuck On
Symptom
The inducer motor runs, but the burners never light, and no error code is displayed.
Gas Supply or Gas Valve Failure
Symptom
The thermostat calls for heat, but the furnace does nothing, and the control board LED is on solid.
No Call for Heat Reaching Control
Symptom
Thermostat goes blank when the furnace starts, then comes back on after a while.
Low Voltage Drop / Transformer Overload
Symptom
Water leaking from around the base of the furnace or onto the floor.
Condensate Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 01 |
The furnace control board shows error code 01, and the unit will not start a heating cycle.
|
Ignition Lockout Due to Recycles Exceeded | View Details |
| 02 |
Error code 02 is displayed, and the furnace inducer motor does not start; there is no ignition sequence.
|
Pressure Switch Stuck Closed | View Details |
| 03 |
Error code 03 is displayed, and the inducer runs continuously, but the burners will not light.
|
Pressure Switch Stuck Open | View Details |
| 04 |
Error code 04 is displayed, and the furnace cycles the inducer and igniter, but the gas valve never opens.
|
Open High Limit Switch | View Details |
| 05 |
Error code 05 is displayed, and the furnace starts then shuts down after a few seconds of flame.
|
Flame Sensed But Lost During Run | View Details |
| 06 |
Error code 06 is displayed, and the furnace blower runs, but the burners will not ignite.
|
Rollout Switch Open | View Details |
| 07 |
Error code 07 is displayed, and the furnace will not respond to the thermostat; there is no inducer or blower operation.
|
Low Voltage Lockout / No 24V from Transformer | View Details |
| 08 |
Error code 08 is displayed, and the indoor blower runs continuously, but no heat call is recognized.
|
Stuck Fan Relay or Fan On After Power Up | View Details |
| 09 |
Error code 09 is displayed, and the furnace attempts to start but shuts down with the blower running for cool-down.
|
Secondary Limit or Auxiliary Limit Open | View Details |
| 10 |
Error code 10: Furnace cycles on and off rapidly without reaching the set temperature.
|
Flame Sense Microampere Out of Range / Nuisance Flame Loss | View Details |
| 11 |
Error code 11: Furnace does not respond to the thermostat; LED indicates an internal control fault.
|
Internal Control Board Failure | View Details |
| 12 |
Error code 12: Furnace starts but shuts down with the inducer and blower running, and no flame is established.
|
Ignition Failure / No Flame Detected | View Details |
| 13 |
Error code 13: Furnace locks out after several failed ignition attempts, requiring a power reset.
|
Ignition Lockout – Repeated Flame Failure | View Details |
| 14 |
Error code 14: Furnace shuts down due to high temperature; the blower runs for an extended cool-down period.
|
Primary Limit Open – Overheat Condition | View Details |
| 15 |
Error code 15: Furnace does not start; LED indicates improper line voltage or polarity.
|
Line Voltage Polarity / Ground Fault | View Details |
| 16 |
Error code 16: Furnace intermittently shuts down; the board indicates flame sensed when there is no call for heat.
|
False Flame Sense / Flame Signal Present with Gas Off | View Details |
| 17 |
Error code 17: Furnace runs the inducer but never proceeds to ignition; the pressure switch error persists.
|
Pressure Switch Did Not Open After Cycle | View Details |
| 18 |
Error code 18: Furnace shuts down with water present in the cabinet or around the base.
|
Condensate Overflow / Drain Blocked | View Details |
| 19 |
Error code 19: Furnace fan runs but there is no heat; the thermostat appears to be calling.
|
Communication Error with Communicating Thermostat | View Details |
| 20 |
Error code 20, and the furnace will not start. The LED indicates a lockout due to too many retries.
|
Hard Lockout – Exceeded Retry Limit | View Details |
| – |
Furnace runs but the carbon monoxide detector alarms or occupants experience headaches.
|
Combustion / Venting Safety Issue | View Details |
| – |
Furnace starts and stops with a loud whooshing or rumbling sound in the vent pipes.
|
Vent Airflow / Resonance Problem | View Details |
| – |
Furnace vibrates excessively and rattles ductwork when running.
|
Mechanical Vibration / Imbalanced Blower | View Details |
| – |
Strong burning or electrical smell when the furnace runs.
|
Overheating Components or Dust Burn-Off | View Details |
| – |
The furnace blower starts but stops after a few seconds, then tries again repeatedly.
|
Blower Motor Overload or Control Issue | View Details |
| – |
The furnace burners light but shut off after 3–10 seconds, repeating several times.
|
Flame Sensor Not Proving Flame | View Details |
| – |
The furnace frequently trips the household circuit breaker.
|
Electrical Overload or Short Circuit | View Details |
| – |
The furnace makes a loud banging or booming noise at startup.
|
Delayed Ignition / Burner Light-Off Problem | View Details |
| – |
The furnace produces a high-pitched whine or squeal during operation.
|
Blower or Inducer Motor Bearing Wear | View Details |
| – |
The furnace runs but some rooms are too hot while others are too cold.
|
Airflow Imbalance / Duct Issues | View Details |
| – |
The furnace runs, but the house never reaches the set temperature, and the supply air feels lukewarm.
|
Underfiring or Low Heat Output | View Details |
| – |
The furnace short cycles, turning on and off frequently without long run times.
|
Short Cycling Due to Overheat or Oversizing | View Details |
| – |
The furnace will not start at all; there are no lights on the control board, and no blower or inducer operation.
|
No Power to Furnace | View Details |
| – |
The indoor blower runs continuously even when the thermostat is not calling for heat or fan.
|
Blower Stuck On | View Details |
| – |
The inducer motor runs, but the burners never light, and no error code is displayed.
|
Gas Supply or Gas Valve Failure | View Details |
| – |
The thermostat calls for heat, but the furnace does nothing, and the control board LED is on solid.
|
No Call for Heat Reaching Control | View Details |
| – |
Thermostat goes blank when the furnace starts, then comes back on after a while.
|
Low Voltage Drop / Transformer Overload | View Details |
| – |
Water leaking from around the base of the furnace or onto the floor.
|
Condensate Leak | View Details |
No matching codes found
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