Boiler shows E07 and stops. Often occurs after a power surge or wiring disturbance. Some relays may click but no normal operation.

Safety first: Isolate the boiler from the mains before opening the control panel. Electronic components are sensitive to static and moisture.

Step-by-step checks:

• 1. Power cycle: Turn off the boiler at the isolator for at least 2 minutes, then restore power. Sometimes transient faults clear after a full reset.
• 2. Inspect wiring: Remove the control panel cover. Check all multi-pin connectors between the display board, main PCB, and sensors. Reseat each connector firmly.
• 3. Look for damage: Examine the PCB for burn marks, swollen capacitors, or signs of water damage. If present, the board must be replaced.
• 4. Verify supply polarity and earth: Ensure live, neutral, and earth are correctly connected at the boiler terminal block. Incorrect polarity can cause control faults on some Viadrus models.
• 5. Surge protection: If E07 occurred after a lightning strike or power surge, consider installing a surge protector and have the PCB tested or replaced.

When to stop: PCB diagnosis and replacement should be carried out by a qualified technician. If E07 persists after basic checks, arrange professional service.