The Baxi E430 fault code — also shown as code 166 on compatible controls — means a temporary water-pressure fault. If E430/166 appears with the crossed-flame symbol, Baxi describes it as a water-pressure test failed.
The wording matters: this is not automatically the same as Baxi E118, which is the low-water-pressure code in the same manufacturer table. Check the display carefully and follow the user guide for the exact model.
What does Baxi E430 mean?
Baxi publishes two related entries:
- E430 / 166: water pressure temporary fault;
- E430 / 166 with crossed-flame symbol: water pressure test failed.
The code reports what the boiler’s controls detected. It does not establish whether the pressure is genuinely low, fluctuating, not being read correctly or failing a model-specific test. An engineer may need to confirm the cause.
Which Baxi boilers can show E430?
Baxi places E430/166 in the error-code group covering Platinum Compact Combi, Duo-tec Compact Combi, Megaflo Compact System, 600 and 800 Combi/System, Duo-tec Combi, Assure Combi/System, Platinum and Platinum+ Combi, Megaflo System and EcoBlue Combi/System.
Confirm the exact model from the user guide or accessible identification label. Other Baxi generations use different pressure codes and controls.
Safe checks you can make
- Photograph the display, including any crossed-flame symbol.
- Check the visible pressure gauge or digital pressure reading.
- Compare it with the normal cold-pressure range stated in your model’s user guide.
- Look for obvious external leaks around radiators and visible pipework.
- Note whether the reading changes sharply or the code returns.
Do not remove the casing, touch a pressure sensor, operate hidden valves or keep adding water. Repeated topping-up can mask a leak or another fault.
Should I repressurise the boiler?
Only use the exact homeowner procedure in the manual for your model, and only if its gauge confirms pressure below the permitted range. Baxi boilers use different filling arrangements.
If the pressure is normal, the code includes the crossed-flame symbol, or the pressure will not stay stable, do not keep filling. Arrange an engineer.
Can I reset E430?
After any permitted pressure correction, use only the model’s stated reset procedure once. Baxi warns that repeated lockout indicates a fault requiring an installer or service engineer.
Is E430 dangerous?
The code is a protective boiler fault, not proof of a gas leak. Leave the casing closed. If water is reaching electrical parts, isolate the appliance only if safe and arrange urgent help.
If you smell gas or a carbon-monoxide alarm sounds, leave the property and use the emergency route. Call 0800 111 999 for a suspected gas leak.
What should I tell the engineer?
Provide the boiler model, full display code and symbols, cold pressure reading, photographs and whether you recently topped up the system. Mention visible leaks or pressure that rises and falls abnormally.
The short answer
Baxi E430/166 means a temporary water-pressure fault; with the crossed-flame symbol it means the water-pressure test failed. Check the gauge and exact manual, but do not repeatedly top up or reset. If the code remains or pressure is unstable, arrange qualified diagnosis.
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