Miller
Miller 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 flashes 1 time repeatedly on the Miller control board.
Ignition Failure / Lockout
2 FLASH
Furnace does not run; status LED on Miller control board flashes 2 times repeatedly.
Pressure Switch Stuck Closed
3 FLASH
Furnace will not ignite; Miller control board LED flashes 3 times in a repeating pattern.
Pressure Switch Stuck Open / Inducer or Venting Problem
4 FLASH
Furnace starts but shuts down quickly; Miller board LED flashes 4 times repeatedly.
Open High Limit Switch / Overtemperature
5 FLASH
Furnace attempts ignition but shuts down; Miller LED flashes 5 times in sequence.
Flame Sensed with Gas Valve Off / False Flame Signal
6 FLASH
Furnace will not start; Miller control board LED flashes 6 times repeatedly.
Rollout Switch Open / Flame Rollout Detected
7 FLASH
Furnace does not respond to thermostat; Miller LED flashes 7 times in a repeating pattern.
Low Flame Sense / Flame Loss During Run
8 FLASH
Furnace cycles on and off or will not start; Miller LED flashes 8 times repeatedly.
Ignition Lockout Due to Repeated Failures
9 FLASH
Furnace will not run; Miller LED flashes 9 times in a repeating pattern.
Line Voltage Polarity or Ground Fault
A1
Miller furnace with advanced digital display shows code A1 and fails to ignite.
Ignition Lockout (Advanced Board)
A2
Miller furnace digital display shows A2; inducer runs but burners do not light.
Pressure Switch Fault (Advanced Board)
A3
Miller furnace digital display shows A3; blower may run but no heat is produced.
High Limit or Auxiliary Limit Open
A4
Miller furnace digital display shows A4; unit may short-cycle or not start.
Flame Sense Error (Advanced Board)
A5
Miller furnace digital display shows A5; blower may run continuously.
Flame Rollout or Manual Reset Limit Open
b0
Miller furnace display shows b0; blower runs but no heat is produced.
Blower On After Power Up / No Call for Heat
E1
Miller furnace digital display shows E1 and shuts down.
Ignition Failure (Retries Exceeded)
E2
Miller furnace digital display shows E2; inducer may run continuously.
Pressure Switch Did Not Open or Close Properly
E3
Miller furnace digital display shows E3; burners light then shut off quickly.
Flame Loss During Run
E4
Miller furnace digital display shows E4; blower may run without heat.
Open Limit or Overheat Lockout
E5
Miller furnace digital display shows E5; unit may not respond to thermostat.
Communication or Internal Control Fault
NO LED
No lights on Miller furnace control board; furnace completely dead.
No Power to Furnace
STEADY ON
Miller furnace status LED is on solid with no flashing, but the furnace does not operate correctly.
Normal Operation Indication / No Call for Heat or Thermostat Issue
Symptom
Furnace blower runs continuously even when thermostat is not calling for heat or fan.
Stuck Blower Relay or Open Limit
Symptom
Furnace cabinet becomes excessively hot to the touch during operation.
Overheating / Inadequate Airflow
Symptom
Furnace cycles on and off rapidly (every few minutes) without reaching set temperature.
Short Cycling Due to Control or Sizing Issues
Symptom
Furnace frequently trips the household circuit breaker.
Electrical Overload or Short Circuit
Symptom
Furnace inducer motor runs but burners do not light and there is a noticeable draft noise.
Draft Established but No Gas Flow
Symptom
Furnace is leaking water into the cabinet or onto the floor.
Condensate Drain Obstruction or Leak
Symptom
Furnace is very noisy in the flue or vent pipe, with whistling or roaring sounds.
Venting Restriction or Resonance
Symptom
Furnace makes loud banging or booming noise at startup.
Delayed Ignition / Burner Light-Off Problem
Symptom
Furnace produces a high-pitched squealing or screeching noise during operation.
Blower or Inducer Bearing Wear
Symptom
Furnace runs but produces no heat; blower operates normally, but supply air is cool.
Burners Not Igniting
Symptom
Furnace runs but some rooms remain cold or have very weak airflow.
Ductwork or Blower Airflow Imbalance
Symptom
Furnace short cycles: burners light for 30–90 seconds, then shut off, then restart repeatedly.
High Limit Cycling / Overheating
Symptom
Furnace starts normally but shuts off when the blower comes on.
Flame Disturbance or Grounding Issue
Symptom
Furnace starts then shuts off after a few seconds without heating the home adequately.
Flame Proving / Sensor Issue
Symptom
Furnace vibrates excessively and causes rattling in ductwork when running.
Mechanical Imbalance or Loose Mounting
Symptom
Furnace will not start at all; thermostat is calling for heat but nothing happens.
No Call Reaching Control / Low-Voltage Circuit Failure
Symptom
Strong burning or electrical smell when the furnace runs.
Overheating Components or Dust Burn-Off
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| 1 FLASH |
Furnace will not start; status LED flashes 1 time repeatedly on the Miller control board.
|
Ignition Failure / Lockout | View Details |
| 2 FLASH |
Furnace does not run; status LED on Miller control board flashes 2 times repeatedly.
|
Pressure Switch Stuck Closed | View Details |
| 3 FLASH |
Furnace will not ignite; Miller control board LED flashes 3 times in a repeating pattern.
|
Pressure Switch Stuck Open / Inducer or Venting Problem | View Details |
| 4 FLASH |
Furnace starts but shuts down quickly; Miller board LED flashes 4 times repeatedly.
|
Open High Limit Switch / Overtemperature | View Details |
| 5 FLASH |
Furnace attempts ignition but shuts down; Miller LED flashes 5 times in sequence.
|
Flame Sensed with Gas Valve Off / False Flame Signal | View Details |
| 6 FLASH |
Furnace will not start; Miller control board LED flashes 6 times repeatedly.
|
Rollout Switch Open / Flame Rollout Detected | View Details |
| 7 FLASH |
Furnace does not respond to thermostat; Miller LED flashes 7 times in a repeating pattern.
|
Low Flame Sense / Flame Loss During Run | View Details |
| 8 FLASH |
Furnace cycles on and off or will not start; Miller LED flashes 8 times repeatedly.
|
Ignition Lockout Due to Repeated Failures | View Details |
| 9 FLASH |
Furnace will not run; Miller LED flashes 9 times in a repeating pattern.
|
Line Voltage Polarity or Ground Fault | View Details |
| A1 |
Miller furnace with advanced digital display shows code A1 and fails to ignite.
|
Ignition Lockout (Advanced Board) | View Details |
| A2 |
Miller furnace digital display shows A2; inducer runs but burners do not light.
|
Pressure Switch Fault (Advanced Board) | View Details |
| A3 |
Miller furnace digital display shows A3; blower may run but no heat is produced.
|
High Limit or Auxiliary Limit Open | View Details |
| A4 |
Miller furnace digital display shows A4; unit may short-cycle or not start.
|
Flame Sense Error (Advanced Board) | View Details |
| A5 |
Miller furnace digital display shows A5; blower may run continuously.
|
Flame Rollout or Manual Reset Limit Open | View Details |
| b0 |
Miller furnace display shows b0; blower runs but no heat is produced.
|
Blower On After Power Up / No Call for Heat | View Details |
| E1 |
Miller furnace digital display shows E1 and shuts down.
|
Ignition Failure (Retries Exceeded) | View Details |
| E2 |
Miller furnace digital display shows E2; inducer may run continuously.
|
Pressure Switch Did Not Open or Close Properly | View Details |
| E3 |
Miller furnace digital display shows E3; burners light then shut off quickly.
|
Flame Loss During Run | View Details |
| E4 |
Miller furnace digital display shows E4; blower may run without heat.
|
Open Limit or Overheat Lockout | View Details |
| E5 |
Miller furnace digital display shows E5; unit may not respond to thermostat.
|
Communication or Internal Control Fault | View Details |
| NO LED |
No lights on Miller furnace control board; furnace completely dead.
|
No Power to Furnace | View Details |
| STEADY ON |
Miller furnace status LED is on solid with no flashing, but the furnace does not operate correctly.
|
Normal Operation Indication / No Call for Heat or Thermostat Issue | View Details |
| – |
Furnace blower runs continuously even when thermostat is not calling for heat or fan.
|
Stuck Blower Relay or Open Limit | View Details |
| – |
Furnace cabinet becomes excessively hot to the touch during operation.
|
Overheating / Inadequate Airflow | View Details |
| – |
Furnace cycles on and off rapidly (every few minutes) without reaching set temperature.
|
Short Cycling Due to Control or Sizing Issues | View Details |
| – |
Furnace frequently trips the household circuit breaker.
|
Electrical Overload or Short Circuit | View Details |
| – |
Furnace inducer motor runs but burners do not light and there is a noticeable draft noise.
|
Draft Established but No Gas Flow | View Details |
| – |
Furnace is leaking water into the cabinet or onto the floor.
|
Condensate Drain Obstruction or Leak | View Details |
| – |
Furnace is very noisy in the flue or vent pipe, with whistling or roaring sounds.
|
Venting Restriction or Resonance | View Details |
| – |
Furnace makes loud banging or booming noise at startup.
|
Delayed Ignition / Burner Light-Off Problem | View Details |
| – |
Furnace produces a high-pitched squealing or screeching noise during operation.
|
Blower or Inducer Bearing Wear | View Details |
| – |
Furnace runs but produces no heat; blower operates normally, but supply air is cool.
|
Burners Not Igniting | View Details |
| – |
Furnace runs but some rooms remain cold or have very weak airflow.
|
Ductwork or Blower Airflow Imbalance | View Details |
| – |
Furnace short cycles: burners light for 30–90 seconds, then shut off, then restart repeatedly.
|
High Limit Cycling / Overheating | View Details |
| – |
Furnace starts normally but shuts off when the blower comes on.
|
Flame Disturbance or Grounding Issue | View Details |
| – |
Furnace starts then shuts off after a few seconds without heating the home adequately.
|
Flame Proving / Sensor Issue | View Details |
| – |
Furnace vibrates excessively and causes rattling in ductwork when running.
|
Mechanical Imbalance or Loose Mounting | View Details |
| – |
Furnace will not start at all; thermostat is calling for heat but nothing happens.
|
No Call Reaching Control / Low-Voltage Circuit Failure | View Details |
| – |
Strong burning or electrical smell when the furnace runs.
|
Overheating Components or Dust Burn-Off | View Details |
No matching codes found
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