Remeha E.04.11 Fault Code: Causes, Fixes & Repair Costs

Common causes

• Dirty or degraded ionisation/ignition electrode Common

  Over time the electrode tip accumulates combustion deposits or becomes physically worn, reducing its ability to either produce a reliable spark or sense the ionisation current from the flame. This is the single most common cause of E.04.11 on Remeha boilers and is addressed during a proper service — Remeha even sells a dedicated service kit that includes a replacement electrode alongside the burner gaskets.

• Failed burner seal or gasket Common

  The burner rope seal (or its newer graphite equivalent) can deteriorate and allow air leakage around the combustion chamber. This disrupts the air-to-gas ratio, making it difficult for the flame to establish or stabilise consistently enough for the ionisation electrode to confirm it. Engineers frequently find this alongside electrode issues on E.04 callouts.

• Faulty ignition transformer Sometimes

  The ignition transformer is responsible for generating the high-voltage spark. If its cabling is damaged or the transformer itself is failing, sparks become weak or intermittent. On Remeha boilers this is a well-known culprit — if replacing the burner gasket does not clear the fault, the transformer is typically the next component to change.

• High-resistance fault in the electrode circuit Sometimes

  A resistor (typically around 1 MΩ) sits in series with the electrode within the PCB or wiring loom. If this component goes open-circuit, the ionisation signal never reaches the controller. Conducting dust on PCB tracks or around the electrode insulator can cause a similar effect. Testing requires disconnecting the electrode and measuring resistance directly.

• Gas supply issue — low pressure or air in the line Sometimes

  If the incoming gas pressure is outside the specified range, or if air has entered the gas pipework (for example after work elsewhere on the system), the burner cannot sustain a stable flame. Confirm other gas appliances in the property are working before assuming a boiler component fault.

• Flue or air-intake obstruction Sometimes

  A blocked or partially obstructed flue outlet or air-inlet terminal prevents proper combustion airflow. Debris, bird nesting material, or ice build-up in winter can all cause this. The boiler may light briefly but the flame will be unstable, leading to repeated ionisation failures.

• Frozen condensate pipe Sometimes

  In cold weather the external section of the condensate drain can ice over, causing condensate to back up into the boiler and trigger a lockout. Although not a direct ignition fault, it can generate an E.04 lockout on some Remeha configurations. The affected pipe will often be visibly iced or frost-covered.

• PCB fault Rare

  If the ionisation signal wiring, electrode, transformer, gas supply, and burner seals all check out correctly, the PCB itself may be misreading or failing to process the ionisation signal. PCB failure is a genuine possibility but should only be concluded after all other causes have been eliminated by a Gas Safe engineer.

How to fix it

1. Check that gas is available at other appliances DIY safe

   Turn on a gas hob or check another gas appliance in the property. If nothing gas-powered is working, the problem is likely with your meter or supply — contact your gas supplier rather than the boiler engineer.

2. Check boiler system pressure DIY safe

   Look at the pressure gauge on the boiler. It should read between 1 and 1.5 bar when cold. If it is below 1 bar, top it up via the filling loop (the braided flexi-hose beneath the boiler) until the needle reaches around 1.2 bar, then close the filling loop valves fully.

3. Check for a frozen condensate pipe (winter months only) DIY safe

   Locate the white plastic condensate pipe that exits the boiler and runs to an external drain. If the exposed section looks iced up, pour warm (not boiling) water along its length until the blockage clears. Dry the pipe and proceed to the reset step.

4. Reset the boiler once DIY safe

   Press and hold the reset button (or follow your model's reset procedure — typically pressing the flame/reset symbol on the front panel) for a few seconds. Allow the boiler a full ignition cycle to attempt to light. If it fires up and runs normally, monitor it over the next day or two. Do not reset more than two or three times in succession — repeated failed attempts will not fix the underlying fault and can be unsafe.

5. Gas Safe engineer: inspect and test the ionisation/ignition electrode Gas Safe engineer

   The engineer will remove the burner assembly, inspect the electrode tip for deposits or wear, measure breakdown resistance to earth, and check the condition of the electrode lead and connector. If dirty, the electrode can be carefully cleaned with fine abrasive paper; if worn or cracked, the electrode should be replaced — ideally using the Remeha service kit part.

6. Gas Safe engineer: inspect and replace the burner seal Gas Safe engineer

   The burner gasket (rope seal on older units, graphite seal on newer ones) should be examined for compression, cracking, or signs of gas bypass. If deteriorated, the complete burner service kit — which includes the electrode, burner gasket, and combustion chamber seals — should be fitted. This is one of the most cost-effective resolutions for a recurring E.04 fault.

7. Gas Safe engineer: check gas supply pressure and purge the line Gas Safe engineer

   The engineer will use a manometer to verify the inlet gas pressure at the gas valve is within the manufacturer's specification. If pressure is correct, the gas supply pipework will be checked for air and purged if necessary. The gas valve itself will be inspected for correct operation.

8. Gas Safe engineer: test the ignition transformer Gas Safe engineer

   If the electrode and seals are serviceable but the fault persists, the transformer wiring and the transformer output voltage will be tested. A failing transformer producing a weak or intermittent spark is a common next cause on Remeha boilers once electrode issues have been ruled out.

9. Gas Safe engineer: check PCB and ionisation circuit Gas Safe engineer

   If all components test correctly, the engineer will check the 1 MΩ series resistor in the ionisation circuit, inspect PCB tracks around the electrode connector for conducting dust or damage, and assess whether the PCB is correctly processing the ionisation signal. PCB replacement is a last resort.

10. Call a Gas Safe registered engineer if the fault persists Gas Safe engineer

    If the DIY checks above have not cleared the fault, or if the boiler locks out again shortly after resetting, book a Gas Safe registered engineer. Ask to see their Gas Safe ID card before any work begins. If your Remeha boiler is relatively recent, check whether it is still within its manufacturer warranty (2 years standard, 5 years on the heat exchanger for Remeha/Baxi-commissioned units) before agreeing to paid repairs.

Parts you may need

• Remeha ignition/ionisation electrode (service kit) · from £45
• Burner graphite seal and combustion chamber gasket set · from £35
• Remeha ignition transformer · from £85
• Remeha PCB (main controller board) · from £320

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