Wiring for flue gas sensor needs checking, possible breakage
The F012 error code on Intergas boilers indicates wiring for flue gas sensor needs checking, possible breakage. Symptoms include shutdown.
Intergas F012 means: wiring for flue gas sensor needs checking, possible breakage. On this component the documented failure modes are flue or air intake blocked or restricted. A Gas Safe registered engineer should diagnose the root cause.
What Does F012 Mean
The F012 code is shown by the boiler’s control board when it detects wiring for flue gas sensor needs checking, possible breakage. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| shutdown. |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 3 different manufacturers.
| Cause |
|---|
| Flue or air intake blocked or restricted |
Safety Warning
F012 is a gas-related fault. Never attempt to repair or adjust the gas valve, burner assembly, or flue system yourself. All gas work must be carried out by a Gas Safe registered engineer (UK) or licensed HVAC technician (US). Repeated resets after ignition failure can cause unburnt gas to accumulate inside the combustion chamber — this is a serious safety hazard. If you smell gas at any point, turn off the gas supply at the meter, open windows, leave the property, and call your gas emergency service immediately. Gas-related fault. Do not open the boiler casing or attempt repairs to the gas valve, burner, ignition or flue. Repeated resets are unsafe. Diagnosis and repair must be carried out by a Gas Safe registered engineer.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Identify which sensor is faulty from the error code (flow, return, DHW, flue gas, or outdoor). 2. Check the wiring — inspect the connections at both the sensor and the PCB for corrosion or loose terminals. 3. Measure the sensor resistance with a multimeter — compare with the manufacturer's resistance/temperature chart (typically 10kΩ at 25°C (77 °F) for NTC sensors). 4. If resistance is out of range (infinite = open circuit, near zero = short circuit), replace the sensor. 5. If resistance is correct, check the wiring continuity between the sensor and PCB. 6. If wiring is good, test the PCB input
How to Fix It
Replace the faulty thermistor/NTC sensor
repair or replace damaged wiring
clean corroded connectors
if the PCB input is damaged, replace the PCB
Inspect the flue and air intake along their whole length, including the outside terminal, and clear any obstruction or debris.
Refer to the Intergas service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Intergas models that can display fault code F012:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Intergas models | — | Possible |
Frequently Asked Questions
Replace the faulty thermistor/NTC sensor. According to the technical documentation, this is the first check on the list for F012.
F012 is classified as a high-severity fault: it involves gas, combustion or flue components. Do not keep resetting the boiler and do not attempt the repair yourself — call a Gas Safe registered engineer.