Intergas 14 Fault Code: Causes, Fixes & Repair Costs
What does the Intergas 14 fault code mean?
Fault code 14 on Intergas boilers indicates that the boiler's PCB has detected a problem with the readings coming from the S1 temperature sensor. The S1 sensor sits on the heat exchanger and monitors the temperature of water leaving it — the flow temperature. When those readings fall outside the boiler's acceptable tolerance range, the boiler locks out and displays code 14 to protect itself from operating in an unsafe or inefficient condition. The root cause could be the sensor itself, a problem with the heat exchanger it monitors, or a PCB that is misreading or not receiving the sensor signal at all.
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
- Faulty or out-of-tolerance S1 sensor Common
The S1 sensor is the most likely culprit. Over time, sensors can drift out of calibration, develop internal faults, or fail outright. When the PCB receives readings that are outside the expected range — or no signal at all — it locks the boiler out as a precaution. Replacing the S1 sensor with a genuine Intergas part is usually the first thing an engineer will try.
- Limescale build-up on the heat exchanger Sometimes
Hard water deposits accumulate on the heat exchanger plates over time. Significant limescale creates hot spots and uneven heat distribution, meaning the S1 sensor reports abnormal temperatures even though the sensor itself is working correctly. If caught early, a power flush or descale can resolve this; if left too long, it can cause the heat exchanger to crack and begin leaking.
- Cracked or failing heat exchanger Sometimes
If limescale has been present for a long time, localised hot spots can physically weaken the heat exchanger and eventually cause it to crack. A cracked heat exchanger may also allow water to escape and damage nearby electronic components. This is a more serious and more costly repair.
- Faulty PCB Rare
The PCB interprets all signals from sensors including S1. If the board has developed a fault — perhaps due to a power surge, moisture ingress, or component failure — it may misread or fail to receive the S1 signal, triggering code 14 even when the sensor and heat exchanger are both in good condition. Engineers can test the PCB with a multimeter to confirm.
How to fix it
- Do not repeatedly reset the boiler DIY safe
Unlike some fault codes where a reset is a reasonable first step, resetting the boiler is not designed to clear an underlying fault code 14. The reset function is intended to be used after the fault has been identified and repaired. Repeatedly resetting a locked-out boiler without addressing the cause risks masking the problem and could cause further damage.
- Check your gas supply is working DIY safe
Before calling an engineer, quickly confirm that other gas appliances in your home (such as your hob or oven) are working normally. If they are not, the issue may be with your gas supply rather than the boiler — contact your gas supplier. If only the boiler is affected, proceed with arranging an engineer visit.
- Engineer to test and replace the S1 sensor if required Gas Safe engineer
A Gas Safe registered engineer will measure the resistance of the S1 sensor against the manufacturer's specification. If the reading is outside tolerance, the sensor should be replaced with a genuine Intergas part. Using non-original sensors can cause further faults or void your warranty. After fitting a new sensor the engineer will reset the boiler and monitor its operation.
- Engineer to inspect and service the heat exchanger Gas Safe engineer
If a new S1 sensor does not clear the fault, the engineer will inspect the heat exchanger for limescale build-up or physical damage. Light to moderate limescale may be addressed with a descale treatment or a full system power flush. A cracked heat exchanger will need to be replaced promptly — water leaking from a crack can quickly damage surrounding electrical components.
- Engineer to test the PCB Gas Safe engineer
If the sensor and heat exchanger are both found to be in acceptable condition, the engineer will use a multimeter to test the PCB for correct power delivery and signal processing. A faulty PCB will need to be replaced. Given the cost of a new PCB, it is worth asking your engineer to discuss whether repair or full boiler replacement makes better financial sense, especially on older units.
- Call a Gas Safe registered engineer Gas Safe engineer
Fault code 14 requires diagnosis and repair by a qualified Gas Safe registered engineer. Do not attempt to access internal boiler components yourself. When booking, mention the specific fault code so the engineer can arrive prepared with the most likely replacement parts, such as an S1 sensor, reducing the number of visits needed.
Parts you may need
- Intergas S1 flow temperature sensor · from £35
- Heat exchanger (model-specific) · from £220
- PCB (printed circuit board, model-specific) · from £180
- Magnetic system filter · from £75
- Scale reducer / inhibitor dosing pot · from £40
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 reset my Intergas boiler to fix fault code 14?
Resetting the boiler will not fix the underlying problem causing code 14. On Intergas boilers the reset function is intended to restart the boiler after a fault has been properly diagnosed and repaired — not as a troubleshooting step in itself. If you reset the boiler and it fires up temporarily before locking out again, the root cause is still present. Call a Gas Safe engineer rather than continuing to reset.
How much does it cost to repair Intergas fault code 14 in the UK?
For the most common repair — replacing the S1 sensor — you can typically expect to pay around £120–£200 including an engineer call-out and the part. If the heat exchanger needs descaling or a power flush the cost usually falls in the £150–£350 range. A full heat exchanger replacement tends to cost around £400 and a PCB replacement is typically in the £400–£500 bracket. If your boiler is older or out of warranty and facing a major component failure, it is worth getting a new boiler quote at the same time, as a full replacement typically costs between £1,500 and £3,000 installed.
What is the S1 sensor on an Intergas boiler and why does it matter?
The S1 sensor is a temperature probe mounted on the heat exchanger that continuously measures the temperature of water flowing out of it. It feeds this data to the PCB, which uses it to control burner operation and keep the boiler running safely. When S1 readings are absent or outside the expected range, the PCB locks the boiler out to prevent overheating or unsafe operation. It is important that only genuine Intergas S1 sensors are used as replacements — non-original parts can cause ongoing faults or invalidate your warranty.
How can I prevent fault code 14 from coming back?
The two most effective preventive measures are having the boiler serviced annually (which also keeps your Intergas warranty valid) and fitting a magnetic system filter if one is not already installed — this catches metallic sludge that can affect sensors and heat exchangers. If you live in a hard water area (most of southern England), fitting a scale reducer and adding a suitable inhibitor to the system water significantly reduces limescale build-up on the heat exchanger, which is the second most common trigger for this fault code.