Common Boiler Problems
Vaillant
BBS Plumbing and Heating, north London are professional Gas Safe Register installers for Vaillant gas boilers and OFTEC registered installers for Vaillant oil-fired boilers. We are also are fully qualified and experienced to service, upgrade and repair all Vaillant boiler types, and carry out repairs to existing hot water and central heating systems.
Combi boilers – ECOtec Plus / Pro and Exclusive
Vaillant Fault Codes
Fault codes have priority over all other displays. If a fault occurs, the display no longer shows the current heating flow temperature. If multiple faults occur at the same time, the display shows the corresponding fault codes for two seconds each in sequence.
| F. Code | Fault |
|---|---|
| F.0 | Interruption to flow NTC (feed temperature sensor) – faulty connection and open circuit. |
| F.01 | Interruption to return NTC (feed temperature sensor) – faulty connection and open circuit. |
| F.10 | Flow NTC (feed temperature sensor) – short circuit. |
| F.11 | Return NTC (feed temperature sensor) – short circuit. |
| F.13 | Tank NTC (feed temperature sensor) – short circuit. |
| F.20 | Safety temperature switch-off by NTC activated |
| F.22 | Dry fire – insufficient water in system – faulty sensor – blocked failed pump. |
| F.23 | Water shortage – temperature difference between flow and return |
| F.24 | Water shortage – temperature rise too quick – pump blocked – failed – NYC faults. |
| F.27 | Incorrect sensing of flame. |
| F.28 | Appliance does not start – ignition or gas supply failure. |
| F.29 | Flame goes out after ignition / during operation – gas supply interrupted / faulty earthing. |
| F.32 | Fan speed variation. |
| F.49 | eBUS under voltage |
| F.60 | Electronic faults. |
| F.61 | Gas-valve control defective. |
| F.62 | Gas valve shut off delay |
| F.63 | EEPROM error. |
| F.64 | Electronics / NTC fault. |
| F.65 | Electronics temperature too high. |
| F.67 | Flame detector input signal is outside the limits. |
| F.70 | No valid DSN in display and/or main board. |
| F.71 | Flow NTC reports constant value. |
| F.72 | Flow and/or return NTC fault. |
| F.75 | No pressure rise detected on pump start up. |
| F.76 | Overheating protection on primary heat exchanger triggered. |
| F.77 | Condensate pump or feedback of accessories blocks heating. |
| F.78 | Wrong configuration. |
| Com | No communication to the main board. |
Please Note: The above error codes all refer to different problems with the boiler and you will need to call an qualified and experienced Gas Safe Potterton service engineer, such as BBS Plumbing and Heating, for further advice.
System boilers – ECOtec System plus
Fault codes have priority over all other displays. If a fault occurs, the display no longer shows the current heating flow temperature. If multiple faults occur at the same time, the display shows the corresponding fault codes for two seconds each in sequence.
| F.Code | Fault |
|---|---|
| F.0 | Interruption to flow NTC (feed temperature sensor) – faulty connection and open circuit. |
| F.01 | Interruption to return NTC (feed temperature sensor) – faulty connection and open circuit. |
| F.02 | Interruption cylinder charging sensor actoSTOR (NTC) only in combination with F.91 |
| F.03 | Interruption cylinder sensor actoSTOR (NTC) only in combination with F.91 |
| F.10 | Flow NTC (feed temperature sensor) – short circuit. |
| F.11 | Return NTC (feed temperature sensor) – short circuit. |
| F.12 | Short circuit at cylinder charging sensor (NTC) only in combination with F.91 |
| F.13 | Tank NTC (feed temperature sensor) – short circuit. |
| F.20 | Safety temperature switch-off by NTC activated |
| F.22 | Dry fire – insufficient water in system – faulty sensor – blocked failed pump. |
| F.23 | Water shortage – temperature difference between flow and return |
| F.24 | Water shortage – temperature rise too quick – pump blocked – failed – NYC faults. |
| F.25 | Safety switch-off: Flue gas temperature too high |
| F.26 | Fault: Gas valve without function |
| F.27 | Incorrect sensing of flame. |
| F.28 | Appliance does not start – ignition or gas supply failure. |
| F.29 | Flame goes out after ignition / during operation – gas supply interrupted – faulty earthing. |
| F.32 | Fan speed variation. |
| F.35 | Air/flue gas duct fault. |
| F.42 | Coding resistor fault (possible in combination with F.70). |
| F.49 | eBUS under voltage. |
| F.52 | Mass flow sensor connection fault. |
| F.53 | Mass flow sensor fault. |
| F.54 | Gas pressure fault (in combination with F.28/F.29). |
| F.56 | Fault: Mass flow sensor regulation. |
| F.57 | Fault during comfort safety mode. |
| F.60 | Electronic faults. |
| F.61 | Gas-valve control defective. |
| F.62 | Gas valve shut off delay |
| F.63 | EEPROM error. |
| F.64 | Electronics / NTC fault. |
| F.65 | Electronics temperature too high. |
| F.67 | Flame detector input signal is outside the limits. |
| 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. |
| F.70 | Invalid DSN in display and/or main board. |
| F.71 | Flow NTC reports constant value. |
| F.72 | Flow and/or return NTC fault. |
| F.73 | Water pressure sensor signal in the wrong range (too low). |
| F.74 | Water pressure sensor signal outside correct range (too high). |
| F.75 | No pressure rise detected on pump start up. |
| F.76 | Overheating protection on primary heat exchanger triggered. |
| F.77 | Condensate pump or feedback of accessories blocks heating. |
| F.78 | Wrong configuration. |
| F.83 | Flow and/or return temperature sensor temperature change fault. |
| F.84 | Fault: Flow/return temperature sensor temperature difference implausible. |
| F.85 | Fault: Flow and return temperature sensors incorrectly fitted. |
| F.92 | Coding resistor fault. |
| F.93 | Gas group fault . |
| Com | No communication to the main board. |
Please Note: The above error codes all refer to different problems with the boiler and you will need to call an qualified and experienced Gas Safe Potterton service engineer, such as BBS Plumbing and Heating, for further advice.
AquaPLUS Gas fired, fan assisted combination boiler
AquaPLUS boilers have an inbuilt advanced multifunction diagnostic display to assist with fault finding in the unlikely event of a boiler malfunction.
- Normal Mode
Under normal conditions the boiler display will show the boiler flow temperature indicating that the boiler is operating correctly after an internal self check.
- Fault Mode
Should a fault develop in the boiler the display will show a fault code indicating what the problem may be- see table below:
| Display Key | |
|---|---|
| 1 | Fan speed malfunction. |
| 2 | Heating demand. |
| 3 | Hot-water demand. |
| 4 | Power store on (Comfort mode). |
| 5 | Pump on. |
| 6 | Gas valve on. |
| 7 | Actual Heating-system flow temperature OR Displaying of a status/error code. |
| 8 | Correct burner operation (normal flame) or lock out (crossed-out flame. |
Error codes
Fault codes take priority over all other display functions in the event of a system fault occurring.
If multiple faults occur, the corresponding fault codes are displayed alternately for about two seconds each – see table below:
| Display | Indication | Cause |
|---|---|---|
| F.00 | Flow-NTC: NTC broken; NTC cable broken; Defective connection at NTC / Defective connection at electronics | Flow-NTC cable defective/broken NTC faulty. |
| F.01 | Return NTC: NTC broken; NTC cable broken. Defective connection at NTC / Defective connection at electronics | Return-NTC cable defective/broken NTC faulty. |
| F.02 | DHW-NTC: NTC broken; NTC cable broken; Defective connection at NTC / Defective connection at electronics. | DHW- NTC cable defective/ broken NTC faulty. |
| F.03 | Tank-NTC: NTC broken; NTC cable broken; Defective connection at NTC / Defective connection at electronics. | Tank- NTC cable defective/ broken NTC faulty. |
| F.10 | Short circuit – flow-NTC | NTC-plug shorted to casing; NTC defective. |
| F.11 | Short circuit – flow-NTC | NTC-plug shorted to casing; NTC defective. |
| F.12 | short circuit DHW- NTC | NTC-plug shorted to casing; NTC defective. |
| F.13 | short circuit DHW- NTC | NTC-plug shorted to casing; NTC defective. |
| F.20 | Over heat cut off activated. | Maximum temperature exceeded. |
| F.22 | Dry fire protection | No water in appliance – pump cable defective – pump blocked or defective – pump output too low. |
| F.23 | Dry fire protection (difference between flow and return NTC’s too large). | No water in appliance – pump cable defective- pump blocked or defective- pump output too low. |
| F.24 | Dry fire protection (temperature gradient of flow NTC too steep). | Air in boiler/system – pump blocked or defective – pump output too low. |
| F.27 | No demand to gas valve. | Electronic board defective; Gas valve defective. |
| F.28 | Boiler goes to lock out. | No gas; Insufficient gas; Incorrect gas valve adjustment; Electrode defective; Ignition lead defect; Electronic igniter defective. |
| F.29 | Flame extinguished re-ignition unsuccessful. | Gas supply absent or insufficient. |
| F.32 | Main heat exchanger anti freeze protection mode due to fan speed deviation too great. | Check fan control cables/connections; Defective fan control cable. |
| F.33 | Main heat exchanger anti freeze protection mode due to no switching signal from the air pressure switch. | Check air pressure switch/fan/fan supply or flue system. |
| F.37 | The rotary speed of the fan is too high or too low. | Air pressure switch defect; fan defect; electronics defect |
| F.41 | No setting for the type of gas is stored. | Set gas type in PCB. |
| F.42 | Faulty cable loom. | Faulty or incorrect loom fitted. |
| F.43 | Faulty cable loom. | Faulty or incorrect loom fitted. |
| F.60 | Electronic fault. | Electronics defect. |
| F.61 | Electronic fault. | Electronics defect. |
| F.62 | Flame rectification present 4 secs. after gas valve turns off. | Check gas valve or burner tubes and injectors or electronics defect. |
| F.63 | EMC fault. | EMC or electronics defect. |
| F.64 | Sensor or electronics fault. | Check NTC’s/connections or electronics defect. |
| F.65 | PCB processor temperature too high. | Check earth connection or electronics defect. |
| F.66 | Display fault. | Display defect; fault in the connection to the display; electronics defect. |
| F.67 | Electronic fault. | Electronics defect. |
The AquaPLUS boiler can also provide a further two diagnostic code displays:
- Status Mode – used to diagnose faults where a fault code is not displayed.
- Diagnostic Mode – to assist with the pinpointing of a particular fault it is possible to use the boiler display in diagnostic mode to interrogate the boiler about the status of certain components.
Please Note: The above error codes all refer to different problems with the boiler and you will need to call an qualified and experienced Gas Safe Potterton service engineer, such as BBS Plumbing and Heating, for further advice.
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