Vaillant Intermittent Electrical / PCB or Sensor Fault

Boiler frequently needs manual reset, with various intermittent fault codes

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Loose internal connections, Moisture ingress, Failing PCB, Unstable mains supply

Safety: Repeated resets without diagnosis can mask a developing fault.

Record codes: Note any fault codes that appear before reset to help diagnosis.
Check environment: Ensure the boiler is not exposed to damp, leaks from above, or extreme temperatures.
Inspect external wiring: Look for loose or corroded connections at the fused spur and control wiring terminals.
Engineer inspection: A professional should open the boiler, check all plug connections, look for signs of overheating or water damage on the PCB, and test sensors.

Hard 4/5

Main Control PCB

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