E6
Vaillant
Compressor Start Failure / Inverter Drive Fault
E6 error, indoor unit operates but no cooling or heating, compressor does not run
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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
Faulty inverter power module on outdoor PCB, Open circuit in compressor wiring harness, Locked rotor compressor, Incorrect phase sequence on three‑phase units
How to Fix / Troubleshooting
Safety: The inverter section carries lethal voltages. Do not touch any components without isolating power and waiting for capacitors to discharge.
- Check wiring harness: With power off, inspect the compressor wiring harness and plug for burns or loose connections. Reseat connectors firmly.
- Listen for start attempts: Restore power and command cooling. If you hear no compressor attempt at all, the inverter PCB may not be driving the compressor.
- Three‑phase check (if applicable): Ensure correct phase sequence and that no phase is missing. This should be done by a qualified electrician.
- Do not bypass protections: Never attempt to hard‑wire the compressor to force it to run; this is dangerous and can cause catastrophic failure.
- Service call: E6 typically requires replacement of the outdoor inverter PCB or compressor after proper diagnostics by a Vaillant technician.
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Repair Difficulty
Professional Required
5/5
Required Part
Outdoor Inverter PCB
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