Overview
D.68 on a Vaillant EcoTEC Plus Regular boiler indicates unsuccessful ignition attempts at the first start-up sequence. In plain terms the boiler attempted to light the burner but the flame did not establish on the initial try. This is a diagnostic message that usually appears when the ignition/safety logic detects no stable flame after the ignition spark and closes down to prevent unburnt gas from flowing. There are two categories of causes: transient/supply issues and component/system faults. Transient causes include a temporary interruption to the gas supply, air in the gas line (for example after work on the gas supply or an emptied meter), or a blocked/fluctuating flue/air intake. Component or wiring causes include failed ignition components (spark generator/transformer, ignition cable, electrode), a faulty gas valve, wiring or PCB faults, or things that affect combustion detection (earth/ionisation fault, condensate blocking the combustion chamber, or recirculation in the flue). Severity ranges from low (a one-off fault caused by a brief gas interruption) to high (persistent ignition failure requiring part replacement). Because ignition and gas control are safety-critical, this is not a DIY repair beyond basic checks and resets — a Gas Safe registered engineer should carry out any work on gas, ignition or internal components.
Possible Cause: Unsuccessful ignitions in the first attempt
Troubleshooting Steps
Safety first
1) If you smell gas: stop using gas appliances, do not operate electrical switches, open windows, leave the property immediately and call your gas emergency number and a Gas Safe engineer. Do not attempt any repairs.
2) If the boiler is displaying D.68 and there is no smell of gas, you can perform safe preliminary checks but do not open the boiler, touch internal components, or attempt to replace gas or ignition parts yourself.
Initial homeowner checks (safe, simple tests)
1) Note the behaviour: is the code intermittent (one-off after a power cut) or persistent every time you call for heat/hot water? Record how many ignition attempts you see and whether the boiler locks out after retries.
2) Check power: confirm the boiler is powered (fused spur and household consumer unit not tripped) and the display is active.
3) Check other gas appliances: does the hob or gas fire work? If all gas appliances are out, contact your gas supplier — this suggests a supply issue.
4) Check boiler pressure: look at the pressure gauge; if pressure is very low (<1.0 bar) restore system pressure per the manual before attempting a reset.
5) Check the condensate discharge: if temperatures are below freezing, the external condensate pipe can freeze and block. If you can safely access the external pipe, inspect for ice or blockages. Thaw gently using warm (not boiling) water and insulated gloves, or call an engineer if you cannot reach it safely.
6) Inspect the flue terminal and air intake (external): visually check for obvious blockages (nests, debris). Do not stick objects into the flue; call a pro if blocked.
7) Reset correctly: only after completing the safe checks above, try a single reset — press and hold the reset button (or follow the boiler manual) for up to 10 seconds. If the boiler still locks out immediately or returns to D.68, do not repeatedly reset — this can hide the underlying fault.
If initial checks do not clear the fault (or if the fault is persistent or accompanied by other symptoms)
1) Do not attempt internal repairs. Call a Gas Safe registered engineer and give them:
- The exact error code (D.68), how often it occurs and any preceding events (power cut, gas work, freezing weather).
- Whether other gas appliances are affected and any visual checks you performed (condensate/pressure/flue).
2) What the engineer will typically check or test (for your understanding):
- Confirm gas supply and working gas pressure at the appliance and meter; check for air in the supply.
- Test ignition system: spark generator/transformer, ignition cable and electrode condition and correct spark gap.
- Check gas valve operation and measure coil resistance (engineers test expected values), and verify gas valve actuation from the PCB.
- Inspect flame sensing/ionisation circuit and earthing; confirm no moisture or condensate in combustion area.
- Inspect wiring harnesses, PCB connections and any sensors that affect start-up.
- Check the flue for recirculation or blockages and inspect condensate removal path.
- Replace faulty components only after proper testing (electrode, ignition transformer, gas valve, harness or PCB as required).
Important warnings and final notes
- Do not attempt to replace ignition electrodes, gas valves, PCBs, or perform gas pressure adjustments yourself. Those tasks must be done by a Gas Safe engineer.
- If the fault appeared after an external event (gas meter work, power cut, or freezing conditions) it may be transient. If the error returns more than once, arrange professional service.
- Keep a record of the fault code, times, and any actions taken — this helps the engineer diagnose the cause faster.
- If you are unsure or the boiler shows additional fault codes, do not delay: contact a Gas Safe registered engineer to inspect and repair the appliance safely.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Vaillant EcoTEC Plus Regular Gas Boiler.