Ruud 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
Status LED shows 1 flash, furnace will not start heating cycle, inducer and blower are off.
Ignition Failure / Lockout (Soft Lockout)
10 FLASHES
Status LED shows 10 flashes, furnace will not start, thermostat appears to call for heat but no response.
Communication Error / IFC Internal Fault
11 FLASHES
Status LED shows 11 flashes, furnace may lock out after several attempts, blower may run.
Limit Switch Lockout / Repeated Limit Trips
12 FLASHES
Status LED shows 12 flashes, furnace may not respond to thermostat or may behave erratically.
Blower Calibration / Blower Fault (ECM models)
13 FLASHES
Status LED shows 13 flashes, furnace may start but shut down on safety, blower may run continuously.
Flame Rollout Lockout
2 FLASHES
Status LED shows 2 flashes, furnace will not start or shuts down quickly after starting.
Pressure Switch Stuck Closed
3 FLASHES
Status LED shows 3 flashes, inducer may start but burners do not light, furnace shuts down.
Pressure Switch Stuck Open / Venting Problem
4 FLASHES
Status LED shows 4 flashes, furnace starts but shuts down shortly after ignition or will not ignite.
Open High Limit Switch / Overtemperature
5 FLASHES
Status LED shows 5 flashes, furnace attempts ignition but burners shut off quickly, then retries.
Flame Sensed with Gas Valve Off / Flame Rollout or Grounding Issue
6 FLASHES
Status LED shows 6 flashes, furnace will not start heating cycle, inducer may run briefly then stop.
Pressure Switch Cycle Lockout / Reversed Polarity or Ground Fault (varies by model)
7 FLASHES
Status LED shows 7 flashes, furnace may start but shuts down, or will not respond to thermostat.
Flame Sense Lockout / Low Flame Signal
8 FLASHES
Status LED shows 8 flashes, furnace will not run, blower may run continuously.
Low Flame Sense or Ignition Lockout (alternate Ruud boards: Line Voltage Fault)
9 FLASHES
Status LED shows 9 flashes, furnace may not respond to thermostat, blower may run unexpectedly.
Reversed Line Polarity / Ground Fault
HARD LOCKOUT
Control board indicates hard lockout (may show solid LED or specific pattern), furnace will not attempt to start until power is cycled.
Hard Lockout Due to Repeated Ignition or Safety Failures
Symptom
Burners light but go out after a few seconds, furnace retries several times then locks out.
Flame Sensing Failure
Symptom
Furnace cabinet vibrates excessively or rattles loudly during operation.
Mechanical Vibration / Loose Components
Symptom
Furnace cycles on and off rapidly (every few minutes) without reaching set temperature; thermostat clicks frequently.
Thermostat Short Cycling or Location Issue
Symptom
Furnace emits a strong metallic, chemical, or electrical burning smell during operation.
Overheating Electrical Component or Contaminant on Heat Exchanger
Symptom
Furnace fan runs but burners never ignite; cool air blows from vents.
No Heat Call or Open Safety Circuit
Symptom
Furnace frequently trips the household circuit breaker.
Electrical Overload or Short Circuit
Symptom
Furnace ignites but produces yellow, lazy flames instead of mostly blue flames.
Improper Combustion
Symptom
Furnace makes loud booming or banging noise at startup when burners ignite.
Delayed Ignition
Symptom
Furnace or ductwork makes loud popping or banging noises shortly after startup or shutdown.
Duct Expansion/Contraction or Overheat Cycling
Symptom
Furnace or vents emit a burning dust smell at the beginning of the heating season.
Dust Burn-Off on Heat Exchanger
Symptom
Furnace produces a high-pitched whine or loud rumbling from the inducer area.
Inducer Motor Bearing Failure or Blocked Inducer Wheel
Symptom
Furnace runs but airflow from vents is weak.
Restricted Airflow
Symptom
Furnace runs but carbon monoxide detector in the home alarms during operation.
Combustion or Venting Problem Producing CO
Symptom
Furnace runs but delivers insufficient heat; house never reaches set temperature.
Low Heat Output
Symptom
Furnace runs but occasionally emits a brief puff of smoke or odor from supply registers at startup.
Minor Combustion Disturbance or Dust in Ducts
Symptom
Furnace starts and runs for a few minutes, then shuts off and restarts frequently (short cycling).
Short Cycling Due to Overheating or Oversizing
Symptom
Furnace starts but shuts down when blower comes on; lights dim or flicker.
Blower Motor Overload or Voltage Drop
Symptom
Furnace will not start after a power outage or brownout.
Control Board Lockup or Surge Damage
Symptom
Furnace will not start at all, no blower, no inducer, no LED lights on control board.
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 do not light, then inducer shuts off and retries.
Ignition System Failure
Symptom
Thermostat calls for heat but furnace does nothing, LED on board is on solid, no inducer or blower.
Thermostat or Low-Voltage Control Circuit Failure
Symptom
Water dripping from metal vent pipe on mid-efficiency Ruud furnace (non-condensing).
Flue Condensation / Improper Venting
Symptom
Water leaking around the base of the furnace or onto the floor, especially on high-efficiency Ruud condensing furnaces.
Condensate Leak
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 1 FLASH |
Status LED shows 1 flash, furnace will not start heating cycle, inducer and blower are off.
|
Ignition Failure / Lockout (Soft Lockout) | View Details |
| 10 FLASHES |
Status LED shows 10 flashes, furnace will not start, thermostat appears to call for heat but no response.
|
Communication Error / IFC Internal Fault | View Details |
| 11 FLASHES |
Status LED shows 11 flashes, furnace may lock out after several attempts, blower may run.
|
Limit Switch Lockout / Repeated Limit Trips | View Details |
| 12 FLASHES |
Status LED shows 12 flashes, furnace may not respond to thermostat or may behave erratically.
|
Blower Calibration / Blower Fault (ECM models) | View Details |
| 13 FLASHES |
Status LED shows 13 flashes, furnace may start but shut down on safety, blower may run continuously.
|
Flame Rollout Lockout | View Details |
| 2 FLASHES |
Status LED shows 2 flashes, furnace will not start or shuts down quickly after starting.
|
Pressure Switch Stuck Closed | View Details |
| 3 FLASHES |
Status LED shows 3 flashes, inducer may start but burners do not light, furnace shuts down.
|
Pressure Switch Stuck Open / Venting Problem | View Details |
| 4 FLASHES |
Status LED shows 4 flashes, furnace starts but shuts down shortly after ignition or will not ignite.
|
Open High Limit Switch / Overtemperature | View Details |
| 5 FLASHES |
Status LED shows 5 flashes, furnace attempts ignition but burners shut off quickly, then retries.
|
Flame Sensed with Gas Valve Off / Flame Rollout or Grounding Issue | View Details |
| 6 FLASHES |
Status LED shows 6 flashes, furnace will not start heating cycle, inducer may run briefly then stop.
|
Pressure Switch Cycle Lockout / Reversed Polarity or Ground Fault (varies by model) | View Details |
| 7 FLASHES |
Status LED shows 7 flashes, furnace may start but shuts down, or will not respond to thermostat.
|
Flame Sense Lockout / Low Flame Signal | View Details |
| 8 FLASHES |
Status LED shows 8 flashes, furnace will not run, blower may run continuously.
|
Low Flame Sense or Ignition Lockout (alternate Ruud boards: Line Voltage Fault) | View Details |
| 9 FLASHES |
Status LED shows 9 flashes, furnace may not respond to thermostat, blower may run unexpectedly.
|
Reversed Line Polarity / Ground Fault | View Details |
| HARD LOCKOUT |
Control board indicates hard lockout (may show solid LED or specific pattern), furnace will not attempt to start until power is cycled.
|
Hard Lockout Due to Repeated Ignition or Safety Failures | View Details |
| – |
Burners light but go out after a few seconds, furnace retries several times then locks out.
|
Flame Sensing Failure | View Details |
| – |
Furnace cabinet vibrates excessively or rattles loudly during operation.
|
Mechanical Vibration / Loose Components | View Details |
| – |
Furnace cycles on and off rapidly (every few minutes) without reaching set temperature; thermostat clicks frequently.
|
Thermostat Short Cycling or Location Issue | View Details |
| – |
Furnace emits a strong metallic, chemical, or electrical burning smell during operation.
|
Overheating Electrical Component or Contaminant on Heat Exchanger | View Details |
| – |
Furnace fan runs but burners never ignite; cool air blows from vents.
|
No Heat Call or Open Safety Circuit | View Details |
| – |
Furnace frequently trips the household circuit breaker.
|
Electrical Overload or Short Circuit | View Details |
| – |
Furnace ignites but produces yellow, lazy flames instead of mostly blue flames.
|
Improper Combustion | View Details |
| – |
Furnace makes loud booming or banging noise at startup when burners ignite.
|
Delayed Ignition | View Details |
| – |
Furnace or ductwork makes loud popping or banging noises shortly after startup or shutdown.
|
Duct Expansion/Contraction or Overheat Cycling | View Details |
| – |
Furnace or vents emit a burning dust smell at the beginning of the heating season.
|
Dust Burn-Off on Heat Exchanger | View Details |
| – |
Furnace produces a high-pitched whine or loud rumbling from the inducer area.
|
Inducer Motor Bearing Failure or Blocked Inducer Wheel | View Details |
| – |
Furnace runs but airflow from vents is weak.
|
Restricted Airflow | View Details |
| – |
Furnace runs but carbon monoxide detector in the home alarms during operation.
|
Combustion or Venting Problem Producing CO | View Details |
| – |
Furnace runs but delivers insufficient heat; house never reaches set temperature.
|
Low Heat Output | View Details |
| – |
Furnace runs but occasionally emits a brief puff of smoke or odor from supply registers at startup.
|
Minor Combustion Disturbance or Dust in Ducts | View Details |
| – |
Furnace starts and runs for a few minutes, then shuts off and restarts frequently (short cycling).
|
Short Cycling Due to Overheating or Oversizing | View Details |
| – |
Furnace starts but shuts down when blower comes on; lights dim or flicker.
|
Blower Motor Overload or Voltage Drop | View Details |
| – |
Furnace will not start after a power outage or brownout.
|
Control Board Lockup or Surge Damage | View Details |
| – |
Furnace will not start at all, no blower, no inducer, no LED lights on control board.
|
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 do not light, then inducer shuts off and retries.
|
Ignition System Failure | View Details |
| – |
Thermostat calls for heat but furnace does nothing, LED on board is on solid, no inducer or blower.
|
Thermostat or Low-Voltage Control Circuit Failure | View Details |
| – |
Water dripping from metal vent pipe on mid-efficiency Ruud furnace (non-condensing).
|
Flue Condensation / Improper Venting | View Details |
| – |
Water leaking around the base of the furnace or onto the floor, especially on high-efficiency Ruud condensing furnaces.
|
Condensate Leak | View Details |
No matching codes found
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