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