Vaillant error codes
Find the meaning of Vaillant fault, warning and status codes, with model context, documented causes, safe checks and links to available manufacturer guidance.
27documented codes
1products and models
1product categories
About Vaillant error codes
An error code is a diagnostic clue, not a complete repair diagnosis. Vaillant may reuse similar-looking codes across different products, model generations or regions, so always confirm the complete code and exact model before following instructions or ordering parts.
This profile connects every indexed Vaillant code to its dedicated explanation page. Each page is structured around the search intent: a quick meaning, symptoms, likely causes, safe troubleshooting, reset guidance, applicable products and the point at which professional help is appropriate. Records marked as verified include the manufacturer or another authoritative technical source.
Start with the code shown on the display, then narrow the result by product or model. Do not assume that a reset has repaired the underlying fault. If a code returns, the product is unsafe, or diagnosis requires internal electrical, gas, refrigerant or moving components, stop and use an authorised technician.
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Popular Vaillant codes
F.88Vaillant · Gas boiler · United KingdomGas-valve electrical connection interruptedThe electrical connection to the gas valve has been interrupted. Vaillant uses F.88 as a diagnostic fault code…F.62Vaillant · Gas boiler · United KingdomDelayed flame switch-offThe flame switch-off was detected after an abnormal delay. Vaillant uses F.62 as a diagnostic fault code across…F.57Vaillant · Gas boiler · United KingdomIncorrect combustion in comfort modeThe boiler is not burning correctly while operating in comfort mode. Vaillant uses F.57 as a diagnostic fault…F.54Vaillant · Gas boiler · United KingdomGas supply faultThe boiler has detected insufficient gas supply, typically alongside F.28 or F.29. Vaillant uses F.54 as a diagnostic…F.53Vaillant · Gas boiler · United KingdomCombustion regulation faultThe combustion-regulation system has detected a fault. Vaillant uses F.53 as a diagnostic fault code across applicable boiler…F.35Vaillant · Gas boiler · United KingdomAir or flue pipe blockedThe boiler has detected a blocked air or flue route. Vaillant uses F.35 as a diagnostic fault code…F.29Vaillant · Gas boiler · United KingdomFlame extinguished during operationThe boiler could not reignite after the flame was lost during operation. Vaillant uses F.29 as a diagnostic…F.28Vaillant · Gas boiler · United KingdomNo flame signal during ignitionNo flame signal was detected during the ignition phase. Vaillant uses F.28 as a diagnostic fault code across…
Vaillant product groups
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F.0Vaillant · Gas boiler · United KingdomFlow temperature sensor interruptedThe electrical signal from the flow temperature sensor is interrupted. Vaillant uses F.0 as a diagnostic fault code…F.1Vaillant · Gas boiler · United KingdomReturn temperature sensor interruptedThe electrical signal from the return temperature sensor is interrupted. Vaillant uses F.1 as a diagnostic fault code…F.10Vaillant · Gas boiler · United KingdomFlow temperature sensor short circuitThe flow temperature sensor circuit has short-circuited. Vaillant uses F.10 as a diagnostic fault code across applicable boiler…F.11Vaillant · Gas boiler · United KingdomReturn temperature sensor short circuitThe return temperature sensor circuit has short-circuited. Vaillant uses F.11 as a diagnostic fault code across applicable boiler…F.12Vaillant · Gas boiler · United KingdomHot-water temperature sensor short circuitThe domestic hot-water connection temperature sensor circuit has short-circuited. Vaillant uses F.12 as a diagnostic fault code across…F.13Vaillant · Gas boiler · United KingdomCylinder temperature sensor short circuitThe cylinder temperature sensor circuit has short-circuited. Vaillant uses F.13 as a diagnostic fault code across applicable boiler…F.20Vaillant · Gas boiler · United KingdomSafety thermal cut-out operatedThe safety thermal cut-out has operated and shut the boiler down. Vaillant uses F.20 as a diagnostic fault…F.22Vaillant · Gas boiler · United KingdomLow system water pressureThe boiler has detected low water pressure in the heating system. Vaillant uses F.22 as a diagnostic fault…F.23Vaillant · Gas boiler · United KingdomFlow and return temperature spread too greatThe temperature difference between the heating flow and return is too great. Vaillant uses F.23 as a diagnostic…F.24Vaillant · Gas boiler · United KingdomTemperature increasing too quicklyThe boiler temperature is increasing more quickly than expected. Vaillant uses F.24 as a diagnostic fault code across…F.25Vaillant · Gas boiler · United KingdomFlue-gas temperature too highThe monitored flue-gas temperature is too high. Vaillant uses F.25 as a diagnostic fault code across applicable boiler…F.27Vaillant · Gas boiler · United KingdomFlame signal detected while burner is offA flame signal has been detected even though the burner should be off. Vaillant uses F.27 as a…F.28Vaillant · Gas boiler · United KingdomNo flame signal during ignitionNo flame signal was detected during the ignition phase. Vaillant uses F.28 as a diagnostic fault code across…F.29Vaillant · Gas boiler · United KingdomFlame extinguished during operationThe boiler could not reignite after the flame was lost during operation. Vaillant uses F.29 as a diagnostic…F.32Vaillant · Gas boiler · United KingdomFan faultThe boiler has detected a fan fault. Vaillant uses F.32 as a diagnostic fault code across applicable boiler…F.35Vaillant · Gas boiler · United KingdomAir or flue pipe blockedThe boiler has detected a blocked air or flue route. Vaillant uses F.35 as a diagnostic fault code…F.52Vaillant · Gas boiler · United KingdomMass-flow sensor faultThe boiler has detected a fault with the mass-flow sensor or Venturi. Vaillant uses F.52 as a diagnostic…F.53Vaillant · Gas boiler · United KingdomCombustion regulation faultThe combustion-regulation system has detected a fault. Vaillant uses F.53 as a diagnostic fault code across applicable boiler…F.54Vaillant · Gas boiler · United KingdomGas supply faultThe boiler has detected insufficient gas supply, typically alongside F.28 or F.29. Vaillant uses F.54 as a diagnostic…F.57Vaillant · Gas boiler · United KingdomIncorrect combustion in comfort modeThe boiler is not burning correctly while operating in comfort mode. Vaillant uses F.57 as a diagnostic fault…F.62Vaillant · Gas boiler · United KingdomDelayed flame switch-offThe flame switch-off was detected after an abnormal delay. Vaillant uses F.62 as a diagnostic fault code across…F.70Vaillant · Gas boiler · United KingdomDevice Specific Number incorrect or missingThe Device Specific Number is missing, incorrect or does not match the coding resistor. Vaillant uses F.70 as…F.72Vaillant · Gas boiler · United KingdomInvalid flow and return sensor spreadThe relationship between the flow and return temperature-sensor readings is invalid. Vaillant uses F.72 as a diagnostic fault…F.75Vaillant · Gas boiler · United KingdomPressure change too low at pump startThe expected pressure change was too low when the heating pump started. Vaillant uses F.75 as a diagnostic…F.83Vaillant · Gas boiler · United KingdomLittle or no temperature rise at burner startLittle or no temperature increase was registered at the flow or return sensor when the burner started. Vaillant…F.84Vaillant · Gas boiler · United KingdomImplausible flow and return temperaturesThe difference between the flow and return temperature readings is implausible. Vaillant uses F.84 as a diagnostic fault…F.88Vaillant · Gas boiler · United KingdomGas-valve electrical connection interruptedThe electrical connection to the gas valve has been interrupted. Vaillant uses F.88 as a diagnostic fault code…