You may have asked for information on a Vaillant fault code. Please take a look at the boiler fault codes below. Don’t worry if you have one of these, it doesn’t necessarily mean your boiler is broken. Your boiler may just need resetting or you have an issue that is easily resolved.
Below we have the fault codes for the ecoTEC Plus series of boilers. You may have different fault codes as they differ across Vaillant boiler models.
Interruption: Flow sensor: NTC plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, NTC defective
Interruption: Return sensor: NTC plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, NTC defective
Interruption: DHW outlet sensor: Only in conjunction with F.91NTC defective, NTC cable defective, defective plug connection on NTC, defective plug connection on the actoSTOR electronics
Interruption: Cylinder sensor: Only in conjunction with F.91NTC defective, NTC cable defective, defective plug connection on NTC, defective plug connection on the actoSTOR electronics
Short circuit: Flow sensor: NTC defective, short circuit in cable harness, cable/casing
Short circuit: Return sensor: NTC defective, short circuit in cable harness, cable/casing
Short circuit: DHW outlet sensor: Only in conjunction with F.91NTC defective, short circuit in cable harness, cable/casing
Short circuit: Cylinder sensor: Combination product: Warm start sensor/cylinder sensor short circuitCombination product with actoSTOR: Short circuit cylinder sensor (NTC) only in combination with F.91NTC defective, short circuit in cable harness, cable/casing
Safety switch-off: Temperature limiter: Incorrect earth connection between cable harness and product, flow or return NTC defective (loose connection), black discharge via ignition cable, ignition plug or ignition electrode
Safety switch-off: Low water pressure: No or insufficient water in the product, water pressure sensor defective
Safety switch-off: Temp.spread too large: Pump blocked, insufficient pump output, air in product, flow and return NTC connected the wrong way round
Safety switch-off: Temp. incr. too fast: Pump blocked, insufficient pump output, air in product, system pressure too low, non-return valve blocked/incorrectly installed
Safety switch-off: Flue temp. too high: Break in plug connection for optional flue gas safety temperature limiter (STB), break in cable harness
Fault: Fuel valve not working: Gas valve stepper motor not connected, multiple plug on the PCB not plugged in correctly, interruption in cable harness, gas valve stepper motor defective, electronics defective
Safety switch-off: Flame simulation: Moisture on the electronics, electronics (flame monitor) defective, gas solenoid valve leaking
Start-up failure: Ignite unsuccessful: Gas meter defective or gas pressure monitor has triggered, air in gas, gas flow pressure too low, thermal isolator device (TAE) has triggered, condensate duct blocked, incorrect gas restrictor, incorrect spare part gas valve, value in D.052 does not correspond to the printed value on the current gas valve, fault on the gas valve, multiple plug on PCB incorrectly plugged in, break in cable harness, ignition system (ignition transformer, ignition cable, ignition plug, ignition electrode) defective, ionisation current interrupted (cable, electrode), incorrect earthing of product, electronics defective
Start-up failure: Ignite unsuccessful: Gas supply temporarily stopped, flue gas recirculation, condensate duct blocked, defective earthing of product, ignition transformer has spark failure
Fault: Fan: Plug on fan not correctly plugged in, multiple plug on PCB not correctly plugged in, break in cable harness, fan blocked, Hall sensor defective, electronics defective
Fault: eBUS: Short circuit on eBUS, eBUS overload or two power supplies with differ- ent polarities on the eBUS
Contact fault mass flow sensor/Venturi: The mass flow sensor/Venturi is not connected electrically – The plug is not plugged in correctly – The plug is not plugged in – The plug is defective – The slot is defective (loose connection) – Mass flow sensor/Venturi defective
Combustion regulation fault: The combustion regulation has detected a fault – Gas flow pressure too low – Liquid gas coding resistance used when operating with natural gas – If the fault occurs again after being cleared: – Gas valve defective – Mass flow sensor/Venturi defective, wet or blocked (if the fault occurs again after being cleared): Do not wet the sensor, do not use any lubricants on the O-ring on the Venturi.
Fault in the gas supply (in combination with F.28/F.29): There is insufficient gas supply to operate the unit – Gas isolator cock(s) closed – Gas flow pressure is too low – Gas valve defective
Safety switch-off: CO limit exceeded: Safety switch-off: CO limit exceededA component in the combustion regulation is defective– Contact fault at the gas valve (plug not plugged in correctly or not plugged in, plug defective, slot is defective (loose connection))– If the fault occurs again after being cleared: The gas valve is defective
Fault: Measuring program: Active comfort protection mode has detected a regulation fault– Ignition electrode highly corroded
Fault: Fuel valve actuation: The gas valve cannot be actuated– Cable harness supply line to the gas valve is defective (short to earth, short circuit)– Gas valve defective– PCB defective
Fault: Fuel valve switch-off delay: Delayed shutdown of gas valve detected– Secondary light (ignition and monitoring electrode indicates delayed extinguishing of the flame signal)– Gas valve defective– PCB defective
Fault: EEPROM: Electronics defective
Fault: Electronics/sensor: Flow or return NTC short circuited, electronics defective
Fault: Electronics temp.: Electronics overheating due to external influences, electronics defective
Fault: Electronics/flame: Implausible flame signal, electronics defective
Fault: Flame signal unstable: Air in gas, gas flow pressure too low, incorrect air ratio, condensate duct blocked, ionisation flow interruption (cable, electrode), flue gas recirculation, condensate duct
Fault: Invalid Device Specific Number: If spare parts fitted: Display and PCB replaced at same time and DSN not reset, incorrect or missing output range coding resistance
Fault: Flow sensor: Flow temperature sensor signalling constant value:– Flow temperature sensor incorrectly positioned at supply pipe– Flow temperature sensor defective
Fault: Flow/return sensor: Flow/return NTC temperature difference too great → flow and/or returntemperature sensor defective
Fault: Water press. sensor: Interruption/short circuit of water pressure sensor, interruption/short circuit to GND in supply line to water pressure sensor or water pressure sensor defective
Fault: Water press. sensor: The line to the water pressure sensor has a short circuit to 5 V/24 V or internal fault in the water pressure sensor
Fault: Pump/ water shortage: Water pressure sensor and/or pump defective, air in the heating installation, insufficient water in the product; connect external expansion vessel to the return