Error D.69

Safety first

- If you can smell gas, do not operate electrical switches or the boiler. Turn off the gas at the appliance isolator or meter, ventilate the area and call your gas emergency service immediately. Do not try to fix gas components yourself.

- Make sure you and others are clear of any obvious hazards. Ensure a working carbon monoxide alarm is fitted near the boiler and in bedrooms.

- If the boiler displays D.69, avoid repeatedly trying to reset the boiler more than once or twice; repeated attempts can mask intermittent faults and won’t fix a component failure.

Initial homeowner checks (safe, quick things you can do)

1. Check mains power: confirm the boiler has power, the fuse hasn’t blown and other electrical supplies are on. A power interruption during ignition can cause failure.

2. Check the gas supply: verify other gas appliances (hob, gas fire) light or check your gas meter and that the gas isolation valve to the boiler is open. If there is no gas to the property, contact your gas supplier.

3. Check boiler pressure: look at the pressure gauge. Normal running pressure is usually around 1.0–1.5 bar. If pressure is very low, top up to the recommended level following the boiler manual, then try a reset once.

4. Check condensate pipe and discharge: in cold weather a condensate pipe can freeze. If the external condensate pipe is frozen or blocked, carefully thaw it with warm (not boiling) water or check for blockages and then try a reset.

5. Check flue and air intake: inspect the external flue terminal and air inlets for obvious blockages (birds’ nests, debris, snow) and remove any safe obstructions. Do not crawl into or dismantle the flue.

6. Reset the boiler: if you have performed the safe checks above, perform a single reset following Vaillant guidance—usually press and hold the reset button for up to 10 seconds. Observe whether the boiler attempts to ignite and whether the D.69 returns.

Further diagnostic notes you can record before calling an engineer

- Note exactly when the fault started and any recent work, service, or weather conditions (freeze).

- Record whether the boiler tried to spark (you may hear a rapid clicking) or was silent during ignition attempts. Note whether the fan started and whether you saw any error codes prior to D.69.

- If the fault follows a power cut, gas supply interruption or blocked condensate, mention that to the engineer; these cause intermittent faults.

What you must not attempt and when to call a professional

- Do not open the boiler casing to probe or replace ignition electrodes, gas valves, transformers, PCBs, wiring or any gas-carrying parts. Work on gas and combustion components must only be done by a Gas Safe-registered engineer.

- If simple checks above do not clear the fault (especially if D.69 returns after reset or you notice intermittent ignition, unusual smells, soot, or poor earthing), arrange a visit by a Gas Safe engineer. Tell them the boiler model (Vaillant EcoTEC Plus regular), the error code (D.69) and what checks you have already performed. The engineer will check gas pressure, ignition electrode and leads, ignition transformer, gas valve operation and resistance, flue and condensate route, earth/earthing, wiring harness and the PCB and will undertake safe repairs or part replacements as required.

Final points

- D.69 is a lockout due to repeated failed ignition attempts and should be treated seriously. Many causes are straightforward to identify (frozen condensate, no gas) but many require specialist testing and replacement of components. Use a Gas Safe-registered engineer for any work beyond the basic checks, and do not guess at repairs to gas or electrical components.