Skip to the content
Trustpilot logo 0800 61 22 302

Vaillant Boiler Fault Codes

Fault code Fault

F.00 / F.0

Flow temperature sensor interruption or not connected

F.01 / F.1

Return temperature sensor interruption or not connected

F.10

Flow NTC short circuit or defective

F.11

Return NTC short circuit or defective

F.20

Safety switch-off temperature limiter - max temperature at the sensor is too high.

F.22

No/low water pressure

F.23

Safety switch-off temperature difference too great 

F.24

Safety switch-off temperature is rising too fast

F.25

Safety switch-off flue gas temperature too high

F.26

Error with gas valve – possible no function

F.27

Safety switch-off flame simulation

F.28

Failure during start-up – ignition unsuccessful to start

F.29

Failure during operation – re-ignition unsuccessful

F.32

Fan error - either defective or not connected

F.49

eBUS error – possible short circuit

F.61

Error with gas valve regulation

F.62

Error with gas valve – switch-off delay

F.63

EEPROM error

F.64

Electronics / NTC error

F.65

Electronic temperature error could be overheating due to external influences

F.67

Electronics flame signal error

F.68

Unstable flame signal error air in gas

F.70

Invalid device-specific number (DSN)

F.71

Flow NTC error – flow temperature sensor signal constant value

F.72

Flow return NTC error – temperature difference too great

F.73

Water pressure sensor signal in the wrong range, it is too low

F.74

Water pressure sensor signal outside correct range, the sensor signal is too high

F.75

Error with pressure – no pressure change detection when starting the pump

F.76

Overheating protection on – primary heat exchanger has responded

F.77

Flue non-return flap condensate pump error

F.78

Interruption to DHW outlet sensor at external controller

F.83

Flow and or return temperature sensor error

F.84

Error with flow/return temperature sensor temperature changing error

F.85

Error with flow and return temperature, sensor incorrectly fitted

CONNECTION

No communication with the PCB (The PCB is what makes all electronic components in your boiler connect)

What is NTC?


An NTC or ‘Negative Temperature Coefficient’ is a type of thermistor (or thermal resistor).

Basically, it’s an electrical component that helps to regulate the temperature of your boiler. So, when you set your heating to a certain temperature it will make sure your boiler stays at that temperature.

Baxi affordable repair combi heat only combi boiler

Safety Warning

When your Vaillant boiler error codes or fault lights flash, don’t do any repair work that involves working with gas as you are required to be Gas Safe Registered by law.

Here at Boiler Plan all our engineers are Gas Safe Registered and will do an amazing job with any Vaillant boiler repair work you may need.

Cosy up with a better boiler company

We exist to be completely transparent – no bull, no waffle, no confusion.