ATAG
ATAG Furnaces Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E0
The furnace does not start; the display shows E0 immediately after power-up.
Control Board Initialization Failure
E1
The furnace attempts to start but shuts down with E1, with no flame established.
Ignition Failure / No Flame Detected
E2
The furnace locks out with E2 shortly after ignition; the flame appears unstable or goes out.
Flame Loss During Operation
E3
The furnace displays E3 and will not start the fan or ignition sequence.
Fan / Air Pressure Switch Fault
E4
The furnace shows E4 and shuts down, often after running for a short time.
Overheat / Safety Thermostat Trip
E5
Furnace displays E5 and will not fire, often accompanied by low or zero system pressure.
Low Water Pressure / Water Pressure Sensor Fault
E6
Furnace shows E6 and stops, often during hot water or heating demand.
Flow Temperature Sensor Fault
E7
Furnace displays E7, often with erratic temperature readings or short-cycling.
Return Temperature Sensor Fault
E8
Furnace shows E8 and will not start; the fan may run briefly then stop.
Flue Gas Temperature Sensor Fault / Overtemperature
E9
Furnace locks out with E9, often after several failed ignition attempts.
Lockout Due to Repeated Ignition Failure
EA
Furnace shows EA; the fan runs but there is no ignition, often associated with air pressure issues.
Air Pressure Switch Not Proving
EC
Furnace displays EC and stops, often during operation rather than at start-up.
Flame Signal Error / Ionisation Fault
F0
Furnace shows F0, with no heating or hot water; the display may be blank or frozen.
User Interface / Display Communication Error
F1
Furnace shows F1 and will not start, often after a power surge or outage.
General Control Board Fault
F2
Furnace shows F2; the fan may run continuously or not at all.
Fan Speed / Tachometer Fault
F3
Furnace displays F3, often with erratic or implausible temperature readings.
Domestic Hot Water (DHW) Temperature Sensor Fault
F4
Furnace shows F4 and stops, often when switching between heating and hot water.
Diverter Valve Position Fault
F5
Furnace displays F5, heating output limited or no heating.
Flow Switch / Flow Sensor Fault
F6
Furnace shows F6, burner shuts down unexpectedly during operation.
Gas Valve Modulation Fault
F7
Furnace displays F7, often with noisy operation or kettling sounds.
Primary Heat Exchanger Temperature Differential Fault
F8
Furnace shows F8, no hot water even though heating may work.
DHW Flow Detection Fault
F9
Furnace displays F9, often with rapid cycling on and off.
Return Temperature Rise Too Fast
Symptom
Condensate water backs up or drips from the furnace casing
Blocked Condensate Trap or Drain
Symptom
External flue terminal drips excessively or stains the wall
Condensate Management / Flue Installation Issue
Symptom
Furnace cycles on and off frequently without maintaining steady temperature
Short Cycling
Symptom
Furnace emits a burning smell or plastic smell during operation
Overheating Electrical Component or Dust Burn-Off
Symptom
Furnace fan runs but burner does not light, no error code displayed
Intermittent Ignition Control Fault
Symptom
Furnace frequently loses pressure and needs topping up.
Chronic System Pressure Loss
Symptom
Furnace is very noisy during operation (whistling, roaring, or droning)
Combustion or Fan Noise
Symptom
Furnace leaks water from the bottom of the casing
Internal Water Leak
Symptom
Furnace makes banging or knocking noises when starting or stopping
Water Hammer / Thermal Expansion Noise
Symptom
Furnace runs but radiators stay cold or only lukewarm.
Poor Heating Performance / Insufficient Flow
Symptom
Furnace shuts down when wind is strong, sometimes with no stored code
Flue Terminal Wind Effect / Combustion Instability
Symptom
Furnace starts then shuts down after a few seconds, radiators only warm at the top
Air in System / Poor Circulation
Symptom
Furnace will not start at all, no display, no lights.
No Power to Appliance
Symptom
Hot water temperature fluctuates or runs hot then cold
Unstable DHW Temperature Control
Symptom
Radiators get hot even when the room thermostat is turned down or off
Uncontrolled Heating / Valve Stuck Open
Symptom
Room thermostat or ATAG controller calls for heat but furnace does not respond
Control Signal / Communication Fault
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E0 |
The furnace does not start; the display shows E0 immediately after power-up.
|
Control Board Initialization Failure | View Details |
| E1 |
The furnace attempts to start but shuts down with E1, with no flame established.
|
Ignition Failure / No Flame Detected | View Details |
| E2 |
The furnace locks out with E2 shortly after ignition; the flame appears unstable or goes out.
|
Flame Loss During Operation | View Details |
| E3 |
The furnace displays E3 and will not start the fan or ignition sequence.
|
Fan / Air Pressure Switch Fault | View Details |
| E4 |
The furnace shows E4 and shuts down, often after running for a short time.
|
Overheat / Safety Thermostat Trip | View Details |
| E5 |
Furnace displays E5 and will not fire, often accompanied by low or zero system pressure.
|
Low Water Pressure / Water Pressure Sensor Fault | View Details |
| E6 |
Furnace shows E6 and stops, often during hot water or heating demand.
|
Flow Temperature Sensor Fault | View Details |
| E7 |
Furnace displays E7, often with erratic temperature readings or short-cycling.
|
Return Temperature Sensor Fault | View Details |
| E8 |
Furnace shows E8 and will not start; the fan may run briefly then stop.
|
Flue Gas Temperature Sensor Fault / Overtemperature | View Details |
| E9 |
Furnace locks out with E9, often after several failed ignition attempts.
|
Lockout Due to Repeated Ignition Failure | View Details |
| EA |
Furnace shows EA; the fan runs but there is no ignition, often associated with air pressure issues.
|
Air Pressure Switch Not Proving | View Details |
| EC |
Furnace displays EC and stops, often during operation rather than at start-up.
|
Flame Signal Error / Ionisation Fault | View Details |
| F0 |
Furnace shows F0, with no heating or hot water; the display may be blank or frozen.
|
User Interface / Display Communication Error | View Details |
| F1 |
Furnace shows F1 and will not start, often after a power surge or outage.
|
General Control Board Fault | View Details |
| F2 |
Furnace shows F2; the fan may run continuously or not at all.
|
Fan Speed / Tachometer Fault | View Details |
| F3 |
Furnace displays F3, often with erratic or implausible temperature readings.
|
Domestic Hot Water (DHW) Temperature Sensor Fault | View Details |
| F4 |
Furnace shows F4 and stops, often when switching between heating and hot water.
|
Diverter Valve Position Fault | View Details |
| F5 |
Furnace displays F5, heating output limited or no heating.
|
Flow Switch / Flow Sensor Fault | View Details |
| F6 |
Furnace shows F6, burner shuts down unexpectedly during operation.
|
Gas Valve Modulation Fault | View Details |
| F7 |
Furnace displays F7, often with noisy operation or kettling sounds.
|
Primary Heat Exchanger Temperature Differential Fault | View Details |
| F8 |
Furnace shows F8, no hot water even though heating may work.
|
DHW Flow Detection Fault | View Details |
| F9 |
Furnace displays F9, often with rapid cycling on and off.
|
Return Temperature Rise Too Fast | View Details |
| – |
Condensate water backs up or drips from the furnace casing
|
Blocked Condensate Trap or Drain | View Details |
| – |
External flue terminal drips excessively or stains the wall
|
Condensate Management / Flue Installation Issue | View Details |
| – |
Furnace cycles on and off frequently without maintaining steady temperature
|
Short Cycling | View Details |
| – |
Furnace emits a burning smell or plastic smell during operation
|
Overheating Electrical Component or Dust Burn-Off | View Details |
| – |
Furnace fan runs but burner does not light, no error code displayed
|
Intermittent Ignition Control Fault | View Details |
| – |
Furnace frequently loses pressure and needs topping up.
|
Chronic System Pressure Loss | View Details |
| – |
Furnace is very noisy during operation (whistling, roaring, or droning)
|
Combustion or Fan Noise | View Details |
| – |
Furnace leaks water from the bottom of the casing
|
Internal Water Leak | View Details |
| – |
Furnace makes banging or knocking noises when starting or stopping
|
Water Hammer / Thermal Expansion Noise | View Details |
| – |
Furnace runs but radiators stay cold or only lukewarm.
|
Poor Heating Performance / Insufficient Flow | View Details |
| – |
Furnace shuts down when wind is strong, sometimes with no stored code
|
Flue Terminal Wind Effect / Combustion Instability | View Details |
| – |
Furnace starts then shuts down after a few seconds, radiators only warm at the top
|
Air in System / Poor Circulation | View Details |
| – |
Furnace will not start at all, no display, no lights.
|
No Power to Appliance | View Details |
| – |
Hot water temperature fluctuates or runs hot then cold
|
Unstable DHW Temperature Control | View Details |
| – |
Radiators get hot even when the room thermostat is turned down or off
|
Uncontrolled Heating / Valve Stuck Open | View Details |
| – |
Room thermostat or ATAG controller calls for heat but furnace does not respond
|
Control Signal / Communication Fault | View Details |
No matching codes found
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