Chaffoteaux 102 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 102 fault code mean?
Fault code 102 on Chaffoteaux boilers indicates a pressure sensor error. In plain terms, the boiler's internal pressure sensor has either detected that the system pressure is outside its safe operating range, or the sensor itself has developed a fault. As a safety precaution, the boiler will typically lock out until the issue is resolved. You may see this described in some manuals as 'Erreur capteur pression' on French-language variants — it refers to exactly the same fault. Note that fault code behaviour can vary slightly between Chaffoteaux models and production years, so always have your full model number to hand when speaking to an engineer.
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
- Low system water pressure Common
The most frequent trigger for this code. If system pressure has dropped below around 1 bar — perhaps after bleeding radiators, a small weep from a fitting, or a slow release through the pressure relief valve — the boiler will lock out to protect itself. Check the pressure gauge on the front panel; it should sit between 1.0 and 1.5 bar when the system is cold.
- Faulty or worn pressure sensor Common
The pressure sensor itself may have deteriorated or developed an internal fault, causing it to report incorrect readings even when the system pressure is perfectly normal. This is a straightforward part swap for an engineer and is typically inexpensive.
- Failing expansion vessel Sometimes
If your pressure keeps dropping and you find yourself topping up the system repeatedly, the expansion vessel is often to blame. When its internal diaphragm fails or the pre-charge air pressure is lost, the system pressure becomes unstable, triggering the sensor error. A weeping pressure relief valve can also cause gradual pressure loss that leads to the same outcome.
- Loose or corroded wiring to the pressure sensor Sometimes
A poor electrical connection at the sensor plug or along the sensor wiring loom can cause intermittent or persistent error codes even when water pressure is adequate. This is more common on older boilers where connections have been exposed to moisture or vibration over time.
How to fix it
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the boiler's front panel. A healthy cold-system reading is between 1.0 and 1.5 bar. If it reads below 1 bar, low pressure is the most likely cause of the fault.
- Repressurise via the filling loop if pressure is low DIY safe
Locate the filling loop — usually a silver or grey braided hose with one or two valves beneath the boiler. Slowly open the valve(s) until the gauge climbs to around 1.2 bar, then close it firmly. Never overfill above 1.5 bar. If you are unsure how your particular filling loop works, check the boiler's user guide or call an engineer.
- Inspect for obvious leaks DIY safe
Walk around your radiators, check visible pipework, and look under the boiler for any signs of dripping water or damp patches. Even a slow weep can cause pressure to drop over days or weeks. If you spot a leak, do not attempt to repair it yourself — contact a Gas Safe engineer.
- Reset the boiler once DIY safe
Press and hold the reset button on the front panel (typically marked with a flame or reset symbol) for a few seconds, then release and wait about 60 seconds for the boiler to restart. If it fires up and runs normally, monitor it over the next 24 hours. If the fault returns, do not keep resetting — repeated lockouts indicate an underlying problem that needs professional diagnosis.
- Call a Gas Safe registered engineer if the fault persists Gas Safe engineer
If the boiler locks out again after a single reset and repressurisation, you need a qualified engineer. They will test the pressure sensor and its wiring, inspect the expansion vessel and pressure relief valve, and replace any faulty components. Do not attempt to access internal boiler parts, the sensor wiring, or any gas components yourself.
Parts you may need
- Water pressure sensor · from £25
- Expansion vessel (replacement) · from £60
- Pressure relief valve (PRV) · from £20
- Filling loop assembly · from £18
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 £100–£280, depending on the underlying cause.
Frequently asked questions
Can I fix Chaffoteaux fault code 102 myself?
You can safely carry out a few checks: look at the pressure gauge, top up the system via the filling loop if it is below 1 bar, and try a single reset. If those steps clear the fault and it does not return, no further action may be needed. However, if the boiler locks out again — or if you suspect a faulty sensor, expansion vessel, or PRV — you will need a Gas Safe registered engineer to diagnose and repair it.
How much does it cost to fix a Chaffoteaux 102 fault in the UK?
Most people with this fault pay somewhere between £100 and £280 all in. A pressure sensor replacement is usually at the lower end (roughly £80–£150 including labour), while an expansion vessel replacement or PRV swap typically falls in the £120–£250 range. If the fault turns out to be PCB-related — which is less common — costs can rise to £300–£450, but that is not the typical outcome for a code 102.
Why does my Chaffoteaux boiler keep losing pressure and showing code 102?
Recurring pressure loss almost always points to one of three things: a slow leak somewhere in the system (check radiator valves, joints, and pipework), a pressure relief valve that is weeping slightly and discharging water, or a failing expansion vessel whose internal diaphragm can no longer absorb pressure changes. An engineer can carry out a pressure test and expansion vessel check to pinpoint the culprit quickly.
Is fault code 102 dangerous?
The fault itself is not a gas safety emergency — it is a pressure monitoring issue that causes the boiler to lock out as a precaution. However, if you smell gas at any point, do not touch any switches or appliances, open windows and doors, leave the property, and call the National Gas Emergency line on 0800 111 999 immediately. That situation is entirely separate from a pressure sensor fault.