BoilerFaultCodes 0
Your boiler is currently running its pump to safely circulate leftover heat, which is a normal part of the cooling process rather than a fault.
Atmos Intersystem HE40 C Fault codes & diagnostics
19 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
System Natural Gas 2004-2018 Discontinued
GC Number 41-249-07
Download the Atmos Intersystem HE40 C manual
PDF
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify. 17 High
2 Low
Just want the most common Atmos Intersystem HE40 C faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 19 documented codes
Tap any card for details
1 Your boiler has successfully reached its target temperature and is now resting as it should.
Your boiler has successfully reached its target temperature and is now resting as it should.
What to check first
- No action required
- The boiler is operating normally
2 Your boiler is currently performing an internal safety check, which is a normal part of its startup process, but it has not progressed past this stage.
Your boiler is currently performing an internal safety check, which is a normal part of its startup process, but it has not progressed past this stage.
Parts commonly replaced
- Control Board
- Wiring Harness
Related codes
4 Your boiler is failing to light the internal flame needed to provide heating or hot water.
Your boiler is failing to light the internal flame needed to provide heating or hot water.
Parts commonly replaced
- Ignition electrode
- Ignition lead
- Gas valve
Related codes
5 Your boiler has detected a problem with the internal sensor that monitors the heating circuit, meaning it cannot reliably provide central heating.
Your boiler has detected a problem with the internal sensor that monitors the heating circuit, meaning it cannot reliably provide central heating.
Parts commonly replaced
- Flow Temperature Sensor
- Return Temperature Sensor
- Wiring Harness
Related codes
6 Your boiler is failing to detect a flame, meaning it cannot stay lit to provide heating or hot water.
Your boiler is failing to detect a flame, meaning it cannot stay lit to provide heating or hot water.
Parts commonly replaced
- Ignition cable
- Spark probe
- Ignition unit
- Controller
Related codes
8 Your boiler has stopped working because the internal fan is moving at the wrong speed or cannot communicate with the main control board.
Your boiler has stopped working because the internal fan is moving at the wrong speed or cannot communicate with the main control board.
Parts commonly replaced
- Fan assembly
- Control PCB
- Wiring harness
Related codes
10 Your boiler has stopped working because one of its internal temperature sensors has detected a fault or a broken connection.
Your boiler has stopped working because one of its internal temperature sensors has detected a fault or a broken connection.
Parts commonly replaced
- Flow Temperature Sensor (S1)
- Sensor Wiring Harness
Related codes
11 Your boiler's internal temperature sensor has stopped working correctly, which prevents the system from knowing how hot the water is.
Your boiler's internal temperature sensor has stopped working correctly, which prevents the system from knowing how hot the water is.
Parts commonly replaced
- S1 Flow Temperature Sensor
- Wiring harness
Related codes
12 Your boiler has stopped working because its main temperature sensor is unable to provide a correct reading to the control board.
Your boiler has stopped working because its main temperature sensor is unable to provide a correct reading to the control board.
Parts commonly replaced
- Flow temperature sensor (S1)
- Wiring harness
Related codes
13 Your boiler has stopped working because one of its internal temperature sensors is not reporting correctly.
Your boiler has stopped working because one of its internal temperature sensors is not reporting correctly.
Parts commonly replaced
- Flow Temperature Sensor (S1)
- Wiring Harness
Related codes
14 Your boiler has stopped working because one of its internal temperature sensors is unable to send a correct reading to the main control board.
Your boiler has stopped working because one of its internal temperature sensors is unable to send a correct reading to the main control board.
Parts commonly replaced
- Flow Temperature Sensor (S1)
- Wiring Harness
Related codes
20 Your boiler has stopped working because its internal temperature sensor is failing to send a correct signal to the control board.
Your boiler has stopped working because its internal temperature sensor is failing to send a correct signal to the control board.
Parts commonly replaced
- NTC Temperature Sensor (S2)
- Sensor wiring harness
Related codes
21 Your boiler has stopped working because one of its internal temperature sensors is providing an incorrect reading or has a faulty connection.
Your boiler has stopped working because one of its internal temperature sensors is providing an incorrect reading or has a faulty connection.
Parts commonly replaced
- NTC Temperature Sensor (S2)
- Sensor wiring harness
Related codes
22 Your boiler has stopped working because one of its internal temperature sensors is providing an incorrect reading or has a faulty connection.
Your boiler has stopped working because one of its internal temperature sensors is providing an incorrect reading or has a faulty connection.
Parts commonly replaced
- NTC Temperature Sensor (S2)
- Sensor wiring harness
Related codes
23 Your boiler has detected a problem with one of its internal temperature sensors, meaning it cannot accurately monitor the water temperature and has stopped working as a safety precaution.
Your boiler has detected a problem with one of its internal temperature sensors, meaning it cannot accurately monitor the water temperature and has stopped working as a safety precaution.
Parts commonly replaced
- NTC Temperature Sensor (S2)
- Sensor wiring harness
Related codes
24 Your boiler has stopped working because one of its internal temperature sensors is providing an incorrect reading or has a faulty connection.
Your boiler has stopped working because one of its internal temperature sensors is providing an incorrect reading or has a faulty connection.
Parts commonly replaced
- NTC Temperature Sensor (S2)
- Wiring Harness
Related codes
29 Your boiler's computer brain has suffered an internal electrical failure and can no longer safely operate the gas supply.
Your boiler's computer brain has suffered an internal electrical failure and can no longer safely operate the gas supply.
Parts commonly replaced
- Main Control PCB
- Gas Valve Relay
Related codes
30 Your boiler's computer board has suffered an internal electrical failure and can no longer safely operate the gas supply.
Your boiler's computer board has suffered an internal electrical failure and can no longer safely operate the gas supply.
Parts commonly replaced
- Main Control Board (PCB)
- Gas Valve