What it means
Vaillant's installation manual calls F.83 a dry fire fault.
What to check, in order
- Check the pressure gauge
Vaillant's ecoTEC plus manual recommends at least 1 bar and says to top up if it falls below 0.8 bar.
- Top up if it's low
Use the filling loop the way your user manual describes, then check the gauge again.
When to call a Gas Safe engineer
If the pressure is fine or F.83 comes back, call a Gas Safe registered engineer. Vaillant also lists a flow or return temperature sensor that isn't sitting correctly on its pipe.
Quick answers
What does the Vaillant F83 fault code mean?
When the burner lit, the boiler's temperature sensors saw almost no change. Vaillant says the usual reason is too little water in the boiler. Vaillant's installation manual calls F.83 a dry fire fault.
Can I fix Vaillant F83 myself?
Easy (about 15 minutes). Start with: check the pressure gauge; top up if it's low. If the pressure is fine or F.83 comes back, call a Gas Safe registered engineer. Vaillant also lists a flow or return temperature sensor that isn't sitting correctly on its pipe.
Is Vaillant F83 worth repairing?
Usually free. Often it's simply low water pressure, which you can top up yourself. If not, an engineer needs to check the sensors.
Checked against
- Vaillant ecoTEC plus open vent installation and servicing instructions (PDF)
- Vaillant ecoTEC plus operating instructions, 2023 edition (PDF)
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.