Vaillant boiler error codes

Founded nearly a century and a half ago, in the 1874, the German company Vaillant is one of the largest manufacturers of heating equipment in Europe. All equipment of Vaillant is certified for work all over the world. Its high performance and reliability is confirmed by over 100 years of operational experience in many countries of the world. The table below lists the boiler Vaillant error codes. Refer to it in case of any malfunction of boilers Vaillant.

Vaillant ecoTEC SERIES boiler error codes

S. 0 No heat demand
S.1 Fan running
S. 2 Water pump running
S. 3 Ignition sequence
S. 4 Burner ignited
S. 5 Fan and pump running
S. 6 Fan over run
S. 7 Pump over run
S. 8 Anti cycling mode
S.10 Hot water demand
S.11 Fan running
S.13 Ignition sequence
S.14 Burner ignited
S.15 Fan and pump running
S.16 Fan over run
S.17 Pump over run
S.20 Warmstart demand
S.21 Fan running
S.22 Pump running
S.23 Ignition sequence
S.24 Burner ignited
S.25 Fan and water pump running
S.26 Fan over run
S.27 Pump over run
S.28 Anti cycling mode
S.30 No heating demand from external controls (clamp 3-4 open)
S.31 Central heating thermostat knob turned off or no heat demand by the eBUS control unit
S.32 Heat exchanger antifreeze active, as fan speed variation is too high. Appliance is within the waiting time of the operation block function
S.34 Antifrost mode active
S.36 No heating demand from low voltage controls (clamp 7-8-9)
S.41 Water pressure > 2,9 bar
S.42 Response from accessory modul or defective condensate pump is blockinq burner operation
S.52 Water pressure > 2,9 bar
S.53 Appliance is within the waiting period of the operation block function due to water shortage (VL-RL spread too big)
S.54 Appliance is within the waiting period of the operation block function due to water shortage (temperature gradient)
S.96 Return-sensor check is running, demand (DHW or heatinq) is blocked
S.97 Water pressure sensor check is running, demand (DHW or heatinq) is blocked
S.98 Flow-/Return-sensor check is running, demand (DHW or heating) is blocked

Vaillant ecoTEC PRO boiler error codes

S.00 Heating: No heat demand
S.02 Heating mode: Pump pre-run
S.03 Heating mode: Ignition
S.04 Heating mode: Burner on
S.06 Heating mode: Fan overrun
S.07 Heating mode: Pump overrun
S.08 Heating, remaining anti-cycling time xx mins
S.10 Domestic hot water requirement via impeller sensor
S.14 DHW mode: Burner on
S.20 Hot water requirement
S.22 DHW mode: Pump pre-run
S.24 DHW mode: Burner on
S.31 No heat demand: Summer mode
S.34 Heating mode: Frost protection
S.46 Comfort protection mode, flame loss at minimum load

Vaillant EcoMax Pro 18/28E boiler error codes

Fault Code Possible Cause
F.1 Lack of gas, a fault with the ignition or flue, or you may need to adjust the gas valve or replace a defective electrode lead.
F.4 Ignition fault.
F.5 The system has suffered a fault due to overheating.
F.6 Your flow NTC (temperature sensor) has developed a fault.
F.17 Check the polarity of your system
F.21 The pump could have failed, over run or there could be an issue with the air lock.

Vaillant Turbomax Plus 824/8E boiler error codes

Codes Possible Cause
F.00 N The flow NTC (Negative Temperature Coefficient Thermostat) cable is either defective or broken and needs replacing.
F.10 Short circuit with the NTC.
F.20 (error solution f20) Your boiler has exceeded the maximum temperature and needs to cool.
(error solution f22)
There is dry fire, low water in the system which is overheating. You may have a defective pump or pump lead.
(error solution f24)
Your pump could be obstructed, at low capacity or there could be trapped air. The pressure of your system could be too low.
(error solution f28)
There is insufficient gas, a defective electrode, ignition lead or electronic ignitor.
F.29(error solution f29) Your flame or pilot light has gone out. Check your flue duck or gas supply to see if there is a problem.
F.60 Your cable loom which connects your gas valve may have short circuited. You could have a defective gas valve or electronic control system.
F.62 Your boiler has exceeded the maximum temperature and needs to cool down.
F.63 This is an electronic fault within your system. An error with your EEPROM (electrically erasable programmable read-only memory.)
F.64 Your flow or backflow NTC has suffered a short circuit or an electronic fault.
F.65 Electronic system temperature too high, potentially due to an external heat source or electrical fault.
F.67 Electronic fault in flame system.

Vaillant boiler error codes

Code Meaning Cause
F.49 eBUS fault Short circuit on the eBUS, eBUS overload or two power supplies with different polarities on the eBUS
F.52 Mass flow sensor connection fault Mass flow sensor not connected/disconnected, plug not connected or incorrectly connected
F.53 Mass flow sensor fault Mass flow sensor faulty, filter below venturi filter cap wet or blocked, gas flow pressure too low
F.54 Gas pressure fault (in combination with F.28/F.29) No or too little gas supply pressure, gas valve closed
F.56 Fault: Mass flow sensor regulation Gas valve defective, cable harness to gas valve defective
F.57 Fault during comfort safety mode Ignition electrode highly corroded
F.61 Fault: Gas valve regulation Short circuit/short to earth in cable harness for the gas valve
Gas valve defective (coils shorted to earth)
Electronic defective
F.62 Fault: Gas valve switch-off delay Delayed shutdown of gas valve
Delayed extinguishing of flame signal
Gas valve leaking Electronics defective
F.63 EEPROM error Electronics defective
F.64 Electronics/NTC fault Supply or return NTC short circuited, electronics defective
F.65 Electronic temperature fault Electronics overheating due to external influences, electronics defective
F.67 Electronics/flame fault Implausible flame signal, electronics defective
F.68 Unstable flame signal fault Air in gas, gas flow pressure too low, wrong air ratio, condensate route blocked, wrong gas restrictor, ionisation flow interruption (cables, electrodes), flue gas recirculation, condensate route
F.70 Invalid device specific number (DSN) Spare part case: Display and PCB replaced at same time and DSN not set, wrong or missing output range coding resistor
F.71 Flow NTC fault Flow temperature sensor signalling constant value:
Flow temperature sensor incorrectly positioned at supply pipe
Flow temperature sensor defective
F.72 Flow/return NTC fault Flow/return NTC temperature difference too great → flow and/or return temperature sensor defective
F.73 Water pressure sensor signal in the wrong range (too low) Interruption/short circuit of water pressure sensor, interruption/short circuit to GND in supply line to water pressure sensor or water pressure sensor defective
F.74 Water pressure sensor signal outside correct range (too low) Cable to water pressure sensor has short-circuitedd at 5V/24 V or internal fault in water pressure sensor
(error f75)
Fault, no pressure change detection when starting pump Water pressure sensor and/or pump defective, air in heating installation, too low water pressure in boiler; check adjustable bypass, connect external expansion vessel to return
F.76 Overheating protection on primary heat exchanger has responded Cable or cable connections for safety fuse in primary heat exchanger or primary heat exchanger defective
F.77 Flue non-return flap/condensate pump fault No response from flue non-return flap or condensate pump defective
F.78 Interruption to DHW outlet sensor at external controller UK link box is connected, but hot water NTC not bridged
F.83 Flow and/or return temperature sesnsor temperature change fault When the burner starts, the temperature change registered at flow and/or return temperature sensor is non-existant or too small.
Not enough water in the boiler
Flow and/or return temperature sensor not in correct position at pipe
F.84 Fault: Flow/return temperature sensor difference implausible Flow and return temperature sensors return implausible values
Flow and return temperature sensors have been inverted
Flow and return temperature sensors have not been correctly fitted
F.85 Fault: Flow and return temperature sensors incorrectly fitted Flow and/or return temperature sensors have been fitted to the same pipe/wrong pipe
F.92 Coding resistor fault The coding resistor on the PCB does not match the entered gas family. Check the resistor, repeat the gas family check and enter the correct gas family.
F.93 Gas group fault Combustion quality outside the permitted range: Wrong gas restrictor, recirculation, wrong gas family, internal pressure measuring point in venturi blocked (do not use lubricant on O-ring in venturi.). Gas family check prematurely terminated.
Communication fault No communication with PCB

Vaillant ecoMAX pro 18E boiler error codes

Code Description Comment
F1 Ignition fault (lockout) Failed to light No gas; Insufficient gas; Incorrect gas valve adjustment; Electrode defect; Ignition lead defect; Electronic igniter defective; Check air inlet duct; Check connections to igniter unit
F4 Ignition fault (lockout) Went out when lit As above
F5 Overheat fault Overheat stat operated; Maximum temperature exceeded;
Check thermistor connections; Air in system with thermistor at maximum setting; Faulty overheat stat connection; Check that pump is wired into appliance and not from programmer. This would cause no pump overrun
F6 Central heating flow NTC fault Flow NTC cable defective/broken NTC faulty
Flow thermistor not fitted correctly, Check pipe work configuration
F10 Central heating return NTC fault Return NTC cable defective/broken NTC faulty Check that thermistor attached correctly to pipe.
F11 No reception by main board Connection fault between main PCB and interface; Faulty interface; Faulty main PCB (processor), Check fan
F12 No reception by the local user interface As F.11
F13 Main board fault As F.11
F14 Central heating flow t? > 95? C System fault; Possible external pump failure; Check NTC on flow Check that pump is wired into appliance and not from programmer. This would cause no pump overrun
F16 Flame detection fault
(flame presence >5 s after burner stop)
Gas valve defective
F17 Power supply <170 V Check electrical supply / polarity, Check fan
F18 Local user interface fault Connections; Faulty interface
F19 Central heating NTC unplugged Check NTC connection
F20 (error solution f20) MMI software incompatible with IRIS software Possible connection fault
(error solution f24)
Central heating return t? >90?C System fault; Possible external pump failure; Check NTC on return; Check that pump is wired into appliance and not from programmer. This would cause no pump overrun.
F25 (error solution f25) Maximum temperature rise slope Possible external pump failure; Air in system restricting movement of water. Insufficient circuit flow
F26 Maximum delta t Check NTC on return; System fault – too restrictive?; Possible pump failure

Vaillant ecoTEC PLUS SERIES boiler error codes

Display Meaning
d.00 Heating partial load
d.01 Water pump return water time for heating mode
d.02 Max. blocking time heating at 20°C Flow temperature
d.03 Drinking water flow temperature reading (800 series only)
d.04 Storage temperature reading (only 600 series)
d.05 Flow temperature target value
d.06 Drinking water temperature target value
d.07 Warm start temperature target value (800 series only) Storage temperaturetarget value (600 series only)
d.08 Room thermostat at terminal 3-4
d.09 Flow target temperature from external analogue regulator to terminal 7-8-9/eBus
d.10 Status internal heating pump
d.11 Status external heating pump
d.12 Status external storage charging pump
d.13 Status external circulation pump
d.22 Hot water request, Terminal C1/C2, impeller
d.25 Storage charging/warm start through warm start clock regulator/release timer
d.40 Flow temperature
d.41 Return temperature
d.47 Outside temperature (with connected VRC 410s)
d.67 Remaining burner locking time
d.76 Appliance variant (device specific number)
d.90 Digital regulator status
d.91 DCF status with connected external probe with DCF77 receiver
d.97 Activation of the second diagnosis level
d.17 Heating flow/return regulation changeover
d.18 Pump mode (return flow)
d.19 Only in ecoTEC plus: Operating modes of the two-stage heating pump
d.26 Changeover option relay to BMU
d.27 Changeover accessory relay 1
d.28 Changeover accessory relay 2
d.30 Control signal for both gas valves
d.33 Fan speed target value
d.34 Fan speed actual value
d.35 Position of priority reverse valve (only 800 series)
d.44 Ionisation current
d.50 Offset for minimum speed
d.60 Number of temperature limiting cut-offs
d.61 Number of fuel automatic system faults
d.64 Average ignition time
d.65 Maximum ignition time
d.68 Successful ignitions in the first attempt
d.69 Successful ignitions in the second attempt
d.70 Set priority-changeover valve position
d.71 Target value max. heating flow temperature
d.72 Pump return flow time after charging an electronically controlled hot water storage (also warm start and charging through C1-C2)
d.73 Offset for warm start target value (only 800 series)
d.75 Maximum charging time for a storage without own controller
d.77 Storage partial load (storage charging capacity limit)
d.78 Storage charging temperature limit (target flow temperature in storage mode)
d.80 Heating operating hours
d.81 Water heating operating hours (800 series only)
d.82 Hystereses in heating mode
d.83 Hystereses in hot water operation
d.84 Maintenance indicator: Number of hours until the next maintenance
d.93 DSN appliance variant setting
d.95 eBus address
d.96 Factory setting
F.00 Flow-NTC:
NTC broken, NTC cable broken. Defective connection at NTC. Defective connection at electronics
F.01 Return-NTC: NTC broken. NTC cable broken. Defective connection at NTC. Defective connection at electronics
F.02 (error solution f2) Drinking water outlet probe stopped (<-10 °C) (800 series only)
F.IO Short circuit – flow-NTC (< 130 °C)
F.11 Short circuit – return-NTC (< 130 °C) NTC defective
F.13 Short circuit in tank sensor
F.20 (error solution f20) Safety temperature limiter addressed
(error solution f22)
Dry fire
F.23 (error solution F23) Water shortage, temperature spread between flow and return probe too large
(error solution f24)
Water shortage, temperature rise too quick
F.25 (error solution f25) Flue gas safety temperature limiter addressed
F.27 Secondary light, the ionisation signal reports a flame in spite of gas valve being turned off
(error solution f28)
Appliance does not start: Attempts to ignite during star failed
F.29(error solution f29) Flame goes off during operation and subsequent ignition attempts failed
F.32 Fan speed variation (too high on start)
F.60 Gas-valve control + defective
F.62 Gas valve shutoff delay defective
F.63 EEPROM error
F.64 Electronics/sensor fault
F.65 Electronics temperature too high
F.70 No valid DSN in Al and/or BMU
F.71 Flow sensor reports constant value
F.72 Flow and/or return sensor fault
F.73 Water pressure sensor or cable harness hydraulics defective
F.74 Water pressure sensor or cable harness defective
(error solution f75)
No sudden change in pressure was detected on turning on the pump
F.76 Overheating protection on primary heat exchanger triggered, damage in primary heat exchanger

Vaillant TURBOmax Plus SERIES boiler error codes

Display Indication Cause
F.00 Flow-NTC: Flow-NTC cable defective/broken NTC faulty
– NTC broken
– NTC cable broken
– Defective connection at NTC
– Defective connection at electronics
F.01 Return-NTC: Return-NTC cable defective/broken NTC faulty
– NTC broken
– NTC cable broken
– Defective connection at NTC
– Defective connection at electronics
F. 10 Short circuit – flow-NTC (< 130 °C) NTC- plug shorted to casing NTC defective
F. 11 Short circuit – return-NTC (< 130 °C)
F.20 (error solution f20) Over heat cut off activated Maximum temperature exceeded
(error solution f22)
Low water or no water in appliance No water in system Pump defective Pump lead defective
F.27 no demand to gas valve Electronic board defective Gas valve defective
(error solution f28)
Boiler goes to lock out No gas Insufficient gas
Incorrect gas valve adjustment Electrode defective Ignition lead defect Electronic igniter defective
F.29(error solution f29) Flame extinguished re-ignition unsuccessful Gas supply absent or insufficient
F.42 Faulty cable loom Faulty or incorrect loom fitted
F.60 to F.67 Irreversible electronic system malfunction Electronic system defective