Vaillant
No Power / Dead Appliance
Water heater will not power on at all; display is blank
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Safety Warning
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.
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Possible Causes
Blown internal fuse, No mains supply to appliance, Faulty on/off switch, Failed main PCB power supply section
How to Fix / Troubleshooting
Safety: Ensure the appliance is isolated before checking internal fuses. Only competent persons should work on electrical circuits.
- Check external supply: Verify that the circuit breaker or fused spur supplying the heater is on and that the fuse has not blown.
- Test mains at appliance: Confirm that mains voltage is present at the appliance terminals.
- Inspect internal fuse: Locate and check the internal fuse on the PCB. Replace only with the exact type and rating specified by Vaillant.
- Check on/off switch: Test continuity of the main power switch and replace if faulty.
- Replace PCB: If supply and fuses are correct but the unit remains dead, the PCB power supply section may have failed and the board should be replaced.
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Repair Difficulty
Hard
4/5
Required Part
Main Control PCB
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