What does the Baxi 600 Series E740 fault code mean?
The E740 fault code on the Baxi 600 Series indicates a “DHW dry fire” condition, which occurs when the boiler attempts to heat domestic hot water (DHW) but detects that there is no water present. This can lead to overheating and potential damage if not addressed promptly.
Common Causes
- Low Water Pressure: Insufficient water pressure can prevent the boiler from detecting water flow, triggering the E740 fault code.
- Blocked or Faulty Diverter Valve: A malfunctioning diverter valve may not allow water to flow correctly to the hot water system, causing the boiler to register a dry fire condition.
Can I fix it myself? (DIY)
If you are comfortable with basic maintenance, check the water pressure gauge on your boiler and ensure it is within the recommended range (typically 1-1.5 bar). If the pressure is low, you can re-pressurise the system using the filling loop. However, for issues related to the diverter valve or any gas/electrical components, it is essential to call a qualified Gas Safe Engineer.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for addressing the E740 fault code could range from £150 to £300, depending on whether the issue is simply low water pressure or if a diverter valve replacement is necessary. A new diverter valve typically costs around £100-£200, plus labour charges.