Vaillant
No Power / Indoor Power Supply Failure
Indoor unit does not power on at all, no display or response to remote
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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
Tripped circuit breaker or blown fuse, Faulty indoor power supply board, Loose live/neutral connections at indoor terminal block, Faulty main switch or isolator
How to Fix / Troubleshooting
Safety: Always turn off the main breaker before opening any electrical covers.
- Check breaker and isolator: Verify that the dedicated AC breaker is ON and that any wall isolator switch is in the ON position.
- Inspect indoor terminal block: Remove the indoor unit’s electrical cover and check that live and neutral wires are firmly secured and not burnt.
- Test outlet voltage: If the unit is plug‑in type, test the outlet with another appliance to confirm power is present.
- Internal fuse: Some Vaillant indoor PCBs have a small fuse. With power off, visually inspect and replace with the same rating if blown.
- If still dead: The indoor power supply / main PCB is likely faulty and should be replaced by a qualified technician.
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Repair Difficulty
Hard
4/5
Required Part
Indoor Main PCB / Power Supply
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