Intergas F000 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas F000 fault code mean?
The F000 code tells you that the boiler's primary heat exchanger temperature sensor — known as S0 — has been detected as defective. This sensor sits directly on the heat exchanger and continuously feeds live temperature readings to the PCB so the boiler can manage combustion safely. When S0 returns a reading that falls outside acceptable limits, or stops responding altogether, the boiler locks out to protect itself from overheating or damage. The fault code will continue to flash on the display until the underlying issue is resolved; a reset is not possible while the sensor remains outside its tolerance range.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Failed S0 sensor Common
The sensor itself has developed an electrical fault, either losing its signal entirely or producing a resistance value so far outside the normal range that the PCB rejects it. This is the most direct cause of F000 and the most frequently confirmed diagnosis when an engineer investigates.
- Loose, disconnected, or damaged wiring Sometimes
The wiring harness connecting S0 to the PCB can work loose over time, corrode at the connector pins, or suffer damage from heat or vibration. A broken circuit here produces the same out-of-range signal as a failed sensor, triggering the same lockout.
- Sensor incorrectly seated on the heat exchanger Sometimes
If S0 is not properly located in its mounting position on the heat exchanger — perhaps following a previous service or repair — it may not make good thermal contact, causing erratic or invalid temperature readings that push the boiler into lockout.
- PCB fault misreading the sensor signal Rare
In a small number of cases the sensor and its wiring check out as electrically sound, but the PCB is failing to interpret the signal correctly. This is comparatively rare but should be considered if a replacement S0 sensor does not clear the fault.
How to fix it
- Check your gas supply is active DIY safe
Before assuming a component fault, confirm that other gas appliances in your home (a gas hob, for example) are working normally. If you have no gas at all, contact your gas supplier rather than a boiler engineer.
- Attempt a single boiler reset DIY safe
Press and hold the flashing Service button on the boiler for approximately two seconds to attempt a reset. If the boiler fires up and runs normally, monitor it closely. If F000 returns within a short time, do not keep resetting — repeated resets will not fix an underlying sensor fault and can mask the problem for an engineer.
- Inspect the wiring to sensor S0 (engineer task) Gas Safe engineer
A Gas Safe engineer will trace the wiring loom from the S0 sensor back to the PCB, looking for loose connector plugs, corroded terminals, chafed insulation, or any obvious break in the circuit. This step alone can resolve the fault if the wiring is found to be at fault rather than the sensor itself.
- Test S0 sensor resistance with a multimeter (engineer task) Gas Safe engineer
The engineer will measure the sensor's resistance at various temperatures and compare the readings against Intergas's published tolerance values. A reading outside the specified range confirms the sensor has failed and needs replacing.
- Reseat the S0 sensor if poorly positioned (engineer task) Gas Safe engineer
If the sensor is found to be incorrectly mounted or has shifted from its proper position on the heat exchanger, the engineer will refit it correctly. This is a straightforward fix but still requires an engineer because it involves working inside the boiler casing.
- Replace the S0 heat exchanger sensor (engineer task) Gas Safe engineer
Where the sensor is confirmed defective, the engineer will fit a genuine Intergas replacement S0 sensor. After fitting, the boiler should be restarted and monitored through a full heating cycle to confirm the fault has cleared and the temperature readings are within normal parameters.
- Investigate the PCB if the fault persists after sensor replacement (engineer task) Gas Safe engineer
If a new S0 sensor does not resolve F000, the engineer should assess whether the PCB is misreading the sensor signal. PCB replacement is a more involved and more costly repair, so a thorough check of all wiring and connections should be completed first to rule out simpler causes.
- Call a Gas Safe registered engineer if you have not already done so DIY safe
F000 is not a homeowner-fixable fault. Every diagnostic and repair step beyond a single reset requires an engineer to work inside the boiler. Contact a Gas Safe registered engineer — or Intergas directly if your boiler is within warranty — to have the fault properly diagnosed and resolved.
Parts you may need
- Intergas S0 heat exchanger temperature sensor · from £35
- Sensor wiring harness / loom · from £25
- Intergas PCB (if sensor fault rules out other causes) · from £220
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£300, depending on the underlying cause.
Frequently asked questions
Can I reset the Intergas F000 fault myself?
You can attempt a single reset by pressing and holding the flashing Service button for about two seconds, but the boiler will lock out again almost immediately if the S0 sensor is genuinely defective. Repeatedly resetting the boiler will not fix the underlying problem and is not recommended. If the fault returns after one reset, call a Gas Safe registered engineer.
How much does it cost to fix an Intergas F000 fault in the UK?
For most people, an F000 repair — covering engineer call-out, diagnosis, and an S0 sensor replacement — comes to somewhere between £120 and £300. The sensor itself is a relatively affordable part; the majority of the cost is labour. If the PCB turns out to be the root cause rather than the sensor, that repair typically costs £400–£500, but this scenario is much less common.
Is the S0 sensor covered under the Intergas warranty?
If your boiler is still within its manufacturer warranty and you have kept up with the annual service requirement, the repair should be covered. Intergas offer warranties ranging from 3 to 10 years, but you must have registered the boiler online within 30 days of installation and maintained the annual service schedule. Contact Intergas directly to confirm your warranty status before arranging a third-party repair.
Why won't my Intergas boiler let me reset it when F000 is showing?
Intergas boilers are designed to prevent a reset while a sensor is still reading outside its acceptable tolerance range. This is a safety feature — the boiler will only accept a reset once the fault condition is no longer active. If the S0 sensor has completely failed, the boiler will refuse to restart regardless of how many times you press the reset button. An engineer needs to repair or replace the sensor before normal operation can resume.