Vaillant Fault Codes
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Vaillant Fault Codes
Boilers covered:
- Vaillant ecoMAX Pro
- Vaillant ecoMAX
- Vaillant ecoMAX Plus
- Vaillant ecoMAX 800
- Vaillant turboMAX Plus
- Vaillant THERMOcompact R3
- Vaillant ecoTEC pro
- Vaillant ecoTEC plus
- Vaillant ecoTEC exclusive
- Vaillant ecoTEC exclusive with Green iQ
- Vaillant ecoTEC sustain
- ecoTEC plus 400 open-vent range
- ecoTEC plus 600 system range
- ecoTEC plus 800 combi range
- Vaillant ecoFIT pure
- Vaillant ecoFIT sustain
- Vaillant ecoTEC plus storage combi
Note: F.22 is often user-fixable (repressurise). Most others need a Gas Safe engineer. Codes can appear with or without the decimal point.
Modern / ecoTEC Range
| Error code | Possible fault | If ticked try the troubleshooter |
|---|---|---|
| F.00 / F.000 | Flow temperature sensor interruption / not connected | ✕ |
| F.01 / F.001 | Return temperature sensor interruption / not connected | ✕ |
| F.02 / F.002 | DHW outlet / cylinder temperature sensor interruption | ✕ |
| F.03 / F.003 | Cylinder / tank temperature sensor interruption | ✕ |
| F.05 | External flue gas sensor interruption | ✕ |
| F.06 | Internal flue gas sensor interruption | ✕ |
| F.10 / F.010 | Flow temperature sensor short circuit | ✕ |
| F.11 / F.011 | Return temperature sensor short circuit | ✕ |
| F.12 | DHW outlet sensor short circuit | ✕ |
| F.13 | Tank / cylinder NTC short circuit | ✕ |
| F.20 | Safety cut-out / overheating (NTC activated) | ✕ |
| F.22 | Low water pressure / dry fire | ✓ |
| F.23 | Excessive temperature differential (flow/return) | ✕ |
| F.24 | Temperature rising too fast / water shortage | ✕ |
| F.25 | Flue gas temperature too high / interruption in thermal module | ✕ |
| F.26 | Gas valve stepper motor fault | ✕ |
| F.27 | Flame detected when none expected / incorrect sensing | ✕ |
| F.28 | Ignition failure (no flame on start-up) | ✓ |
| F.29 | Flame loss during operation | ✓ |
| F.32 | Fan fault / incorrect fan speed | ✕ |
| F.33 | Fan frost protection / air pressure switch | ✕ |
| F.49 | eBUS communication / voltage fault | ✕ |
| F.52 | Mass flow sensor fault | ✕ |
| F.53 | Combustion regulation fault | ✕ |
| F.54 | Insufficient gas pressure | ✕ |
| F.61 | Gas valve control fault | ✕ |
| F.62 | Gas valve switch-off delay | ✕ |
| F.63 | EEPROM fault | ✕ |
| F.64 | Electronics / sensor / ADC fault | ✕ |
| F.65 | Electronics temperature too high | ✕ |
| F.67 | Flame signal on return | ✕ |
| F.68 | Unstable flame signal | ✕ |
| F.70 | Invalid device specific number | ✕ |
| F.71 | Flow sensor position fault | ✕ |
| F.72 | Flow and return temperature sensor fault / difference | ✕ |
| F.73 | Pressure sensor signal too low | ✕ |
| F.74 | Pressure sensor signal too high | ✕ |
| F.75 | No pressure change detected when pump starts | ✓ |
| F.76 | Thermal fuse fault | ✕ |
| F.77 | Condensate pump or flue flap fault | ✕ |
| F.78 | External sensor fault | ✕ |
| F.83 | No temperature rise detected after burner lights | ✕ |
| F.84 | Flow/return temperature difference / sensors swapped | ✕ |
| F.85 | Flow/return sensors swapped or fault | ✕ |
| S.53 | Status: waiting due to excessive flow/return spread | ✕ |
Classic / Related Ranges
Many of the F. codes above also apply to earlier atmoTEC, turboTEC and similar models. Confirm with the specific handbook for older units.