Water heater is completely dead; no display, no lights, no response.

Safety: Only qualified persons should work on mains voltage circuits.

• Check breaker and switch: Verify that the circuit breaker feeding the Weishaupt water heater is on and that any local isolation switch is turned on.
• Test outlet or supply: Use a known-good appliance or a multimeter to confirm power is present at the supply point.
• Inspect mains terminals: With power off, remove the front cover and check that the live, neutral, and earth wires are securely clamped in the terminal block.
• Internal fuse: Many Weishaupt boards have an internal fuse. If accessible, check and replace only with the exact same type and rating. If it blows again, a deeper fault exists.
• Board replacement: If supply and fuse are good but the unit remains dead, the control board power supply is likely defective and requires replacement.