De Dietrich Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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A01
Burner does not ignite; the furnace attempts ignition then locks out with A01 on the display.
Ignition Failure Lockout
A02
Burner lights briefly then goes out; repeated attempts lead to an A02 lockout on the display.
Flame Loss During Operation
A03
Boiler stops with A03, burner off; the overheat symbol may be lit.
Safety Overheat Thermostat Tripped
A04
Boiler displays A04 and will not start, often after a power interruption.
Low Water Pressure / Water Shortage
A05
Boiler shows A05; the fan may run briefly then stop, with no ignition.
Air Pressure Switch / Flue Safety Fault
A06
Display shows A06, boiler stops, often associated with domestic hot water demand.
Flow Sensor / DHW Sensor Fault
A07
Boiler displays A07, heating stops, flow temperature reading abnormal.
Flow Temperature Sensor Fault
A08
Boiler shows A08, no heating, return temperature reading abnormal.
Return Temperature Sensor Fault
A09
Boiler locks out with A09, often after long operation at high temperature.
Flue Gas Overtemperature / Safety Thermostat
A10
Boiler shows A10, burner off, fan may continue to run.
Flame Detection Error (False Flame or No Flame Signal)
A11
Boiler displays A11, no ignition, fan may not start.
Fan Start Failure
A12
Boiler shows A12, intermittent burner operation, sometimes with noise from the fan.
Fan Speed / Airflow Regulation Fault
A13
Boiler displays A13, no heating, pump symbol may flash.
Circulation Pump Fault
A14
Boiler shows A14, heating limited or stopped, often with high return temperature.
Insufficient Circulation / Delta T Fault
A15
Boiler displays A15, no response to thermostat, heating demand not recognized.
External Control / Thermostat Communication Fault
A16
Boiler displays A16, domestic hot water priority fault, DHW not available.
3-Way Valve / Diverter Valve Fault
A17
Boiler displays A17, no hot water from storage tank, but heating may work.
Cylinder Temperature Sensor Fault
A18
Boiler displays A18, burner output limited, possible modulation issues.
Gas Valve Modulation Fault
A19
Boiler displays A19, anti-freeze or low temperature protection fault.
Frost Protection / Low Temperature Sensor Fault
A20
Boiler displays A20, general safety lockout, no specific sub-code.
General Safety Lockout
E01
Control panel displays E01, boiler unresponsive, display may be blank or frozen.
Main PCB / Control Board Fault
E02
Boiler displays E02, no display backlight or intermittent display.
User Interface / Display Board Fault
E03
Boiler displays E03, external safety device open (e.g., flue thermostat, safety chain).
External Safety Circuit Open
E04
Boiler displays E04, condensate alarm, boiler stops.
Condensate Drain Fault
E05
Boiler displays E05, gas supply error, no ignition.
Gas Supply / Gas Valve Error
E06
Boiler displays E06, communication error with remote controller or cascade manager.
BUS Communication Fault
E07
Boiler shows E07, external sensor fault (e.g., outdoor sensor).
Outdoor Temperature Sensor Fault
E08
Boiler displays E08, expansion vessel / pressure fluctuation fault.
Expansion Vessel / Pressure Regulation Fault
E09
Boiler shows E09, safety valve discharge detected (if sensor fitted) or frequent pressure drops.
Safety Valve / Overpressure Fault
E10
Boiler displays E10, internal temperature sensor or limit fault.
Internal Boiler Temperature Monitoring Fault
Symptom
Domestic hot water temperature fluctuates between too hot and too cold during a shower.
Unstable DHW Temperature Control
Symptom
Furnace causes frequent tripping of the household circuit breaker or RCD.
Electrical Short or Earth Leakage
Symptom
Furnace condensate pipe drips or gurgles loudly, with occasional water backing up into the boiler.
Condensate Drainage Problem
Symptom
Furnace emits a high-pitched whistling or howling noise during operation.
Combustion Resonance / Gas Flow Noise
Symptom
Furnace frequently cycles on and off with short run times, causing wear and noise.
Short Cycling
Symptom
Furnace is leaking water from the bottom of the casing.
Internal Water Leak
Symptom
Furnace is running but radiators are only lukewarm, and the house does not reach the set temperature.
Underheating / Insufficient Output
Symptom
Furnace makes loud banging or knocking noises when starting or stopping.
Water Hammer / Thermal Expansion Noise
Symptom
Furnace produces a burning or plastic smell when running.
Overheating Electrical Component or Dust Burn-off
Symptom
Furnace produces a strong smell of gas near the unit, especially at startup or shutdown.
Gas Leak or Incomplete Ignition
Symptom
Radiators are hot at the top but cold at the bottom; the furnace runs continuously.
Sludge / Poor Heat Transfer in Emitters
Symptom
The furnace does not respond to the room thermostat, staying off even when there is demand.
Control Signal Not Reaching Boiler
Symptom
The furnace runs but some radiators remain completely cold.
System Imbalance / Air Lock
Symptom
The furnace starts normally but shuts down after a few minutes without an error code.
Soft Lockout / Demand Loss
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| A01 |
Burner does not ignite; the furnace attempts ignition then locks out with A01 on the display.
|
Ignition Failure Lockout | View Details |
| A02 |
Burner lights briefly then goes out; repeated attempts lead to an A02 lockout on the display.
|
Flame Loss During Operation | View Details |
| A03 |
Boiler stops with A03, burner off; the overheat symbol may be lit.
|
Safety Overheat Thermostat Tripped | View Details |
| A04 |
Boiler displays A04 and will not start, often after a power interruption.
|
Low Water Pressure / Water Shortage | View Details |
| A05 |
Boiler shows A05; the fan may run briefly then stop, with no ignition.
|
Air Pressure Switch / Flue Safety Fault | View Details |
| A06 |
Display shows A06, boiler stops, often associated with domestic hot water demand.
|
Flow Sensor / DHW Sensor Fault | View Details |
| A07 |
Boiler displays A07, heating stops, flow temperature reading abnormal.
|
Flow Temperature Sensor Fault | View Details |
| A08 |
Boiler shows A08, no heating, return temperature reading abnormal.
|
Return Temperature Sensor Fault | View Details |
| A09 |
Boiler locks out with A09, often after long operation at high temperature.
|
Flue Gas Overtemperature / Safety Thermostat | View Details |
| A10 |
Boiler shows A10, burner off, fan may continue to run.
|
Flame Detection Error (False Flame or No Flame Signal) | View Details |
| A11 |
Boiler displays A11, no ignition, fan may not start.
|
Fan Start Failure | View Details |
| A12 |
Boiler shows A12, intermittent burner operation, sometimes with noise from the fan.
|
Fan Speed / Airflow Regulation Fault | View Details |
| A13 |
Boiler displays A13, no heating, pump symbol may flash.
|
Circulation Pump Fault | View Details |
| A14 |
Boiler shows A14, heating limited or stopped, often with high return temperature.
|
Insufficient Circulation / Delta T Fault | View Details |
| A15 |
Boiler displays A15, no response to thermostat, heating demand not recognized.
|
External Control / Thermostat Communication Fault | View Details |
| A16 |
Boiler displays A16, domestic hot water priority fault, DHW not available.
|
3-Way Valve / Diverter Valve Fault | View Details |
| A17 |
Boiler displays A17, no hot water from storage tank, but heating may work.
|
Cylinder Temperature Sensor Fault | View Details |
| A18 |
Boiler displays A18, burner output limited, possible modulation issues.
|
Gas Valve Modulation Fault | View Details |
| A19 |
Boiler displays A19, anti-freeze or low temperature protection fault.
|
Frost Protection / Low Temperature Sensor Fault | View Details |
| A20 |
Boiler displays A20, general safety lockout, no specific sub-code.
|
General Safety Lockout | View Details |
| E01 |
Control panel displays E01, boiler unresponsive, display may be blank or frozen.
|
Main PCB / Control Board Fault | View Details |
| E02 |
Boiler displays E02, no display backlight or intermittent display.
|
User Interface / Display Board Fault | View Details |
| E03 |
Boiler displays E03, external safety device open (e.g., flue thermostat, safety chain).
|
External Safety Circuit Open | View Details |
| E04 |
Boiler displays E04, condensate alarm, boiler stops.
|
Condensate Drain Fault | View Details |
| E05 |
Boiler displays E05, gas supply error, no ignition.
|
Gas Supply / Gas Valve Error | View Details |
| E06 |
Boiler displays E06, communication error with remote controller or cascade manager.
|
BUS Communication Fault | View Details |
| E07 |
Boiler shows E07, external sensor fault (e.g., outdoor sensor).
|
Outdoor Temperature Sensor Fault | View Details |
| E08 |
Boiler displays E08, expansion vessel / pressure fluctuation fault.
|
Expansion Vessel / Pressure Regulation Fault | View Details |
| E09 |
Boiler shows E09, safety valve discharge detected (if sensor fitted) or frequent pressure drops.
|
Safety Valve / Overpressure Fault | View Details |
| E10 |
Boiler displays E10, internal temperature sensor or limit fault.
|
Internal Boiler Temperature Monitoring Fault | View Details |
| – |
Domestic hot water temperature fluctuates between too hot and too cold during a shower.
|
Unstable DHW Temperature Control | View Details |
| – |
Furnace causes frequent tripping of the household circuit breaker or RCD.
|
Electrical Short or Earth Leakage | View Details |
| – |
Furnace condensate pipe drips or gurgles loudly, with occasional water backing up into the boiler.
|
Condensate Drainage Problem | View Details |
| – |
Furnace emits a high-pitched whistling or howling noise during operation.
|
Combustion Resonance / Gas Flow Noise | View Details |
| – |
Furnace frequently cycles on and off with short run times, causing wear and noise.
|
Short Cycling | View Details |
| – |
Furnace is leaking water from the bottom of the casing.
|
Internal Water Leak | View Details |
| – |
Furnace is running but radiators are only lukewarm, and the house does not reach the set temperature.
|
Underheating / Insufficient Output | View Details |
| – |
Furnace makes loud banging or knocking noises when starting or stopping.
|
Water Hammer / Thermal Expansion Noise | View Details |
| – |
Furnace produces a burning or plastic smell when running.
|
Overheating Electrical Component or Dust Burn-off | View Details |
| – |
Furnace produces a strong smell of gas near the unit, especially at startup or shutdown.
|
Gas Leak or Incomplete Ignition | View Details |
| – |
Radiators are hot at the top but cold at the bottom; the furnace runs continuously.
|
Sludge / Poor Heat Transfer in Emitters | View Details |
| – |
The furnace does not respond to the room thermostat, staying off even when there is demand.
|
Control Signal Not Reaching Boiler | View Details |
| – |
The furnace runs but some radiators remain completely cold.
|
System Imbalance / Air Lock | View Details |
| – |
The furnace starts normally but shuts down after a few minutes without an error code.
|
Soft Lockout / Demand Loss | View Details |
No matching codes found
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