Intergas 24 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas 24 fault code mean?
Fault code 24 on an Intergas boiler indicates a problem with the S2 temperature sensor. This falls within the S2 sensor fault group (codes 20–24), all of which relate to the boiler's controller detecting an abnormal or out-of-range signal from the S2 sensor. The S2 sensor monitors the return or secondary heat exchanger temperature depending on your model, and the boiler needs a reliable reading from it to operate safely. When the reading falls outside acceptable limits — or disappears entirely — the controller locks the boiler out and displays the fault code. The fault LED above the reset key will flash; pressing the key restarts the boiler once the underlying issue is resolved. If you want to re-check which fault was stored, turn the boiler off and hold the Service button — the last fault code will reappear on the display.
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 or out-of-range S2 sensor Common
The sensor element itself may have developed an open circuit, short circuit, or a resistance value outside its normal operating range. This is the single most common trigger for code 24 and usually means the sensor needs replacing. Only genuine Intergas parts should be used, as incorrect sensors can cause further damage.
- Loose, corroded, or damaged sensor wiring Common
The wiring harness running to the S2 sensor can suffer from corrosion at the connector pins, chafing against the boiler casing, or a pulled terminal. Even a slight increase in resistance caused by a corroded connector can push the signal outside the controller's acceptable window and trigger the lockout.
- Sensor not properly seated or incorrectly installed Sometimes
If the S2 sensor has been disturbed during a previous service or repair and not refitted correctly, it may give inconsistent readings. Intergas manuals explicitly warn that incorrect sensor fitment can cause serious damage, so proper installation is essential.
- Limescale or sludge fouling around the sensor Sometimes
In hard water areas, limescale deposits can build up around the sensor pocket, insulating the sensor from the water temperature it is supposed to read. Heavy sludge in the system can have a similar masking effect, causing the sensor to report inaccurate temperatures.
- PCB fault causing misreading of sensor signal Rare
If the sensor and its wiring both check out correctly, the PCB may be misinterpreting the signal. This is a less common cause but should be investigated by an engineer after the sensor and wiring have been ruled out.
How to fix it
- Note the fault code carefully on the display before doing anything else DIY safe
Intergas boilers display the fault code on the temperature readout with the fault LED flashing. If the code has disappeared, switch the boiler off and press the Service button to recall the last stored fault. Confirming it is code 24 (rather than a nearby code such as 20–23) will help any engineer you contact.
- Check the boiler is not in an obvious error state first DIY safe
Make sure the boiler's gas supply is turned on, the system pressure is between 1 and 1.5 bar, and there are no other fault codes being displayed alongside code 24. Resolve any low-pressure issue via the filling loop before attempting a reset.
- Attempt a single boiler reset DIY safe
Press the reset key (the key symbol on the controller) once to restart the boiler. If the boiler fires up and runs normally, monitor it closely. If code 24 returns within a short time or immediately, do not keep resetting — further resets without fixing the root cause will not help and could mask a developing fault.
- Arrange for a Gas Safe registered engineer to test the S2 sensor Gas Safe engineer
The engineer will use a multimeter to check the resistance of the S2 sensor against Intergas's published specifications. If the reading is out of range or shows an open or short circuit, the sensor will be replaced. Only genuine Intergas replacement parts should be fitted.
- Have the engineer inspect the S2 sensor wiring and connectors Gas Safe engineer
Even if the sensor itself passes the resistance test, the engineer will check each connector and the wiring run for signs of corrosion, pinching, or loose terminals. A wiring repair or connector clean is often a quicker and cheaper fix than a full sensor replacement.
- Ask the engineer to check for limescale or sludge fouling Gas Safe engineer
Particularly in hard water areas, the engineer may find scale build-up in the sensor pocket. They can advise whether a system flush or descale is warranted at the same time, which can prevent the fault recurring.
- If sensor and wiring are both confirmed good, have the PCB investigated Gas Safe engineer
A PCB fault is the least common cause but cannot be ruled out if everything else tests correctly. PCB diagnostics and replacement must be carried out by a Gas Safe engineer, as this work involves the boiler's control circuitry.
- Call a Gas Safe registered engineer if the fault persists or you are unsure Gas Safe engineer
If code 24 keeps returning after a reset, or you have not been able to identify the cause through the checks above, contact a Gas Safe registered engineer. You can verify an engineer's registration at www.gassaferegister.co.uk using the licence number on the back of their ID card. Before booking, check whether your Intergas boiler is still under its manufacturer warranty — Intergas offers warranties of between 3 and 10 years depending on the model and registration, which could cover the repair at no cost to you.
Parts you may need
- Intergas S2 temperature sensor · from £45
- Sensor wiring harness / connector set · from £25
- Intergas PCB (control board) · 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–£350, depending on the underlying cause.
Frequently asked questions
Can I just keep resetting my Intergas boiler to clear fault code 24?
Resetting once to see if the fault was a one-off blip is reasonable, but repeated resets without fixing the underlying S2 sensor issue will not solve the problem. If code 24 returns after a reset, the boiler needs a proper diagnosis from a Gas Safe engineer. Repeatedly locking out and resetting can also obscure fault history data that helps an engineer diagnose the root cause quickly.
Is my Intergas boiler covered under warranty for a fault code 24 repair?
Possibly, yes. Intergas boilers come with a standard 12-month warranty, but many models carry extended cover of 3 to 10 years when properly registered. If your boiler is within its warranty period and has been serviced regularly, the S2 sensor replacement or repair may be covered at no charge. Check your original warranty documentation or contact Intergas directly with your model and serial number before booking a paid repair.
What is the S2 sensor on an Intergas boiler and where is it located?
The S2 sensor is a thermistor — a temperature-measuring resistor — used by the boiler's controller to monitor the return or secondary heat exchanger water temperature, depending on your specific model. Its exact position varies slightly between the Combi Compact HRE and ECO RF ranges, but it is always located internally within the boiler casing and is not accessible to a homeowner without dismantling the appliance. A Gas Safe engineer will know its precise location for your model.
Could fault code 24 mean the PCB needs replacing, and how much does that cost?
A PCB fault is a possible but uncommon cause of code 24 — an engineer will only suspect it after confirming the S2 sensor and its wiring are both in good condition. PCB replacement on an Intergas boiler typically costs £280–£450 including parts and labour, which is significantly more than a sensor swap at around £120–£200 all-in. For this reason, a good engineer will always test the sensor first. If your boiler is out of warranty and the PCB has failed, it is also worth getting a boiler replacement quote for comparison, particularly on older units.