Johnson & Starley 26 Fault Code: Causes, Fixes & Repair Costs
What does the Johnson & Starley 26 fault code mean?
Fault code 26 on Johnson & Starley WarmCair warm air heaters is a collective safety lockout code displayed as 'E26' on the LCD panel. It indicates that the boiler's ESYS control board has detected one or more serious internal errors and has shut the unit down as a precaution. The fault can stem from a wide range of underlying issues grouped together in the control system's diagnostic table, including flame circuit failure, valve feedback errors, flow or return thermistor faults, EEPROM lockout, ADC lockout, exhaust gas temperature too high, flue temperature sensor lockout, condensate pump float switch activation, low mains power supply, and remote reset lockout. In practice, field engineers most often trace E26 to flame detection problems — particularly a loose flame sensing electrode lead — or to ESYS module wiring faults.
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
- Loose or disconnected flame sensing electrode lead Common
The flame sensing electrode lead may not be fully pressed onto its tag on the ESYS module, breaking the electrical connection. This is one of the most frequently reported real-world causes of E26, and can also trigger error 1 alongside it. Even a partially seated connector can cause intermittent or total flame detection failure, causing the board to lock the unit out.
- Flame sensing or gas circuit fault Common
A faulty or contaminated flame sensor, unstable gas supply pressure, or a failing gas valve can all cause the control board to lose confirmation that the burner is alight. The unit shuts down as a safety measure. Low gas pressure from the supply network or a partially closed gas cock can also contribute.
- ESYS control board wiring fault Common
Over time, wiring connections to and from the ESYS module can loosen, corrode, or sustain damage. This can produce inaccurate readings from multiple parts of the system simultaneously, explaining why E26 covers such a broad cluster of sub-faults. Damaged wire insulation or a short circuit can mimic sensor and valve failures.
- Flow or return thermistor failure Sometimes
Both the flow thermistor and the return thermistor are specifically listed within the E26 fault cluster. If either sensor drifts out of calibration or fails outright, the ESYS board cannot reliably monitor heat exchanger temperatures and will lock out the appliance.
- Condensate pump or float switch fault Sometimes
The WarmCair range is known to be susceptible to condensate-related issues. A blocked condensate drain, a failing condensate pump, or a triggered safety float switch will cause the control board to register a lockout condition. Blocked or kinked condensate pipework is a common seasonal problem in colder weather.
- Fan fault or flue blockage Sometimes
The air circulation fan must run at full speed for safe combustion. A failing fan motor, a partially obstructed flue, or a blocked heat exchanger can restrict airflow, leading to exhaust gas temperatures exceeding the safe threshold and triggering the E26 lockout.
- EEPROM or ADC lockout on the control board Rare
Internal memory (EEPROM) corruption or an analogue-to-digital converter (ADC) fault within the ESYS board itself can trigger E26 without any external component failure. This points to a degraded or failed control board rather than a peripheral sensor or wiring issue.
How to fix it
- Check that the gas supply is on and the boiler is receiving power DIY safe
Confirm the gas isolation cock at the meter and at the appliance are both fully open. Check the relevant fuse or circuit breaker in your consumer unit has not tripped. These are the only gas-supply checks a homeowner should carry out.
- Attempt a single reset using the LCD panel DIY safe
If the display shows 'LOCKOUT', press the Reset button on the WarmCair's LCD user control panel. Allow the unit to complete its ignition sequence. If it fires up and runs normally, monitor it closely over the next few hours. If E26 returns, do not keep resetting — repeated resets without a repair can mask a worsening fault.
- Check the condensate drain for blockages (homeowner check) DIY safe
Inspect the visible condensate pipework for obvious blockages, kinks, or signs of freezing in cold weather. If you suspect a frozen condensate pipe, you may carefully apply warm (not boiling) water to the external section to thaw it. Do not attempt to access the internal condensate pump or float switch — these require an engineer.
- Engineer: inspect the flame sensing electrode lead and ESYS connections Gas Safe engineer
A Gas Safe registered engineer should begin by checking that the flame sensing electrode lead is fully and securely pressed onto its tag on the ESYS module. All wiring connectors to the board should be inspected for corrosion, damage, and secure seating, as loose connections are a primary cause of E26.
- Engineer: check ignition electrode condition, spark gap, and gas valve operation Gas Safe engineer
The engineer should inspect the ignition electrode for cracks or carbon deposits and verify the spark gap is set to 4 mm. The gas valve should be tested for correct operation, and gas supply pressure should be measured and confirmed stable during burner firing.
- Engineer: test flow and return thermistors Gas Safe engineer
Both thermistors should be resistance-tested against the manufacturer's temperature-resistance curve. A sensor reading outside specification should be replaced. Wiring continuity between each sensor and the ESYS board should also be verified.
- Engineer: inspect heat exchanger condition Gas Safe engineer
The engineer should remove the burner and air circulation fan to gain access. By introducing a light source through the burner chamber and inspecting through the fan opening, they can identify cracks, sooting, or heat exchanger degradation that could be causing combustion or temperature faults.
- Engineer: check the air circulation fan and flue Gas Safe engineer
The air circulation fan must run at maximum speed. If mains voltage is present at the motor but the fan is not running at full speed, the fan motor should be replaced. The flue should be checked for blockages or restriction that could cause exhaust gas temperatures to exceed the safe limit.
- Engineer: inspect the condensate pump and float switch Gas Safe engineer
The engineer should verify the condensate pump is operating correctly, check the power supply to the pump, and inspect for blockages in the drain path. The safety float switch should be tested for correct operation and continuity.
- Engineer: evaluate the ESYS control board if all other components test satisfactory Gas Safe engineer
If all sensors, wiring, gas components, fan, and condensate system check out correctly, the ESYS control board itself may have an internal EEPROM or ADC fault. Board replacement or specialist repair may be required.
- Call a Gas Safe registered engineer if you have not already done so DIY safe
Fault code E26 covers a range of serious safety-related faults that cannot be diagnosed or repaired by a homeowner. All repair work on gas components, control boards, sensors, and the condensate pump must be carried out by a Gas Safe registered engineer familiar with Johnson & Starley WarmCair warm air heaters.
Parts you may need
- ESYS control board (WarmCair C Range) · from £280
- Flame sensing electrode · from £35
- Flow thermistor · from £25
- Return thermistor · from £25
- Condensate pump · from £75
- Air circulation fan motor · from £120
- Gas valve · from £180
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 £150–£450, depending on the underlying cause.
Frequently asked questions
Can I fix Johnson & Starley fault code 26 myself?
No. While you can safely try a single reset using the LCD panel and check that your gas supply is on, E26 signals a serious internal fault that requires professional diagnosis. The official guidance from Johnson & Starley is clear that fault codes on WarmCair appliances cannot be resolved by the homeowner — a warm air technician or Gas Safe registered engineer must be called. Attempting to work on gas components, the ESYS board, or internal wiring yourself is unsafe and illegal under the Gas Safety (Installation and Use) Regulations 1998.
Why does fault code 26 cover so many different problems?
On the WarmCair C Range, E26 is a collective or category code rather than a single-fault indicator. The ESYS control board groups a range of serious safety conditions — including flame circuit failure, valve feedback errors, thermistor faults, ADC lockout, EEPROM corruption, condensate pump activation, and flue overtemperature — under the same displayed code. This means an engineer needs to work through a structured diagnostic checklist to identify which specific underlying fault has triggered the lockout. The most frequently found cause in the field is a loose flame sensing electrode lead on the ESYS module.
How much will it cost to repair a Johnson & Starley E26 fault in the UK?
For the most common repairs — wiring connections, a faulty sensor, or a condensate pump — you can typically expect to pay between £150 and £450 including parts, labour, and VAT. More involved work such as a gas valve replacement or a new ESYS control board will push costs toward the higher end of that range or beyond. Heat exchanger replacement, which is rare but possible if the unit is heavily corroded, can cost £500 or more and at that point it is worth comparing the repair cost against a replacement unit. Prices in London and the South East tend to run 20–35% higher than the national average.
My WarmCair keeps showing E26 and resetting clears it temporarily — is that safe?
Repeatedly resetting the boiler without addressing the underlying fault is not a safe long-term approach. A recurring E26 typically means the fault is intermittent rather than resolved — common causes include a flame sensing lead that makes contact sometimes but not reliably, or a thermistor that is drifting in and out of specification. Allowing the boiler to keep locking out and resetting can stress other components and delay identification of a potentially worsening fault. Limit resets to two or three attempts and then arrange for an engineer to inspect the unit before using it further.