Baxi E430 fault codewhat it means and how to fix it
A temporary water-pressure fault on the 600, 800 and Compact family, from Baxi's professional error-code table. If it comes with a crossed flame symbol the pressure self-test has failed.
Take care
Get a Gas Safe registered engineer to look at your Baxi E430
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
Is there a crossed-out flame symbol with it?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
Just E430, no flame symbol
A temporary pressure fault. Check the gauge and top up if it is under 1 bar; it may clear on its own.
If it persists with the gauge above 1 bar, book an engineer for the pressure switch and wiring.
E430 with a crossed flame
Baxi list this as "water pressure test failed" — the boiler ran its check and the reading did not respond as it should.
Engineer visit. It is a diagnostic rather than a repair you can do from the front panel.
What E430 means
E430 is on Baxi's professional error-code page but not in the printed 600, 800 or Compact tables, which is why a reader who has just been through the manual has not found it. Baxi give two entries: "E430 / 166 — Water pressure temporary fault", and "E430 / 166 + Flame 'crossed' — Water pressure test failed". The "/ 166" is the older two-digit rendering of the same fault on boards that could not show a number above 255, and it is worth knowing only so that a 166 in an old service note does not send you looking for a different problem.
Read alongside E118, the shape is clear enough. E118 is the boiler saying the pressure is under 0.5 bar; E430 is the boiler saying it could not get a sensible reading, or that the reading did not behave as expected when the pump ran. The first thing to do is what you would do for E118 — check the gauge, top up if it is low, and see whether the code clears — because a system right at the bottom of the range can produce either.
If the gauge is fine and E430 stays, the hydraulic pressure switch, its wiring to the PCB, or the board itself is where an engineer will look, and the 600 Combi fault-finding flow for the pressure circuit (5 V DC at connector X22, then the switch) is the sequence they will follow. Baxi do not print a homeowner action for E430; the user guides say a code not in the table means "contact Baxi Customer Support".
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Pressure at the bottom of the range | A system sitting around 0.5 to 0.7 bar can give the board an inconsistent reading as the pump starts and the pressure dips. Topping up to 1 to 1.5 bar removes the ambiguity. | Common |
| Pressure switch wiring or connector | A loose or corroded connection at the switch or at PCB connector X22 gives the board a signal that comes and goes, which is what a "temporary fault" reads as from the outside. | Common |
| Hydraulic pressure switch failing | The switch is a mechanical device in the water circuit and can stick or chatter. The 600 and 800 use Baxi part 5114748; the fault-finding flow ends with its replacement. | Occasional |
| PCB not reading the input | If the 5 V feed to the switch is missing the board cannot see the switch at all. Baxi's flow says check for approximately 5 V DC between green and black at X22 before condemning anything else. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£0–£250
Time on site
45 minutes
Free if topping up clears it. Hydraulic pressure switch (Baxi 5114748) fitted around £120–£180. A PCB, if the 5 V feed is missing, £250 or more.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Baxi / Potterton / Main hydraulic pressure switch (600, 800, Assure, Eco Compact)
5114748£40–£90Authorised Baxi parts distributor
Price checked 28 September 2026
Baxi / Potterton / Main main PCB
£150–£320Authorised Baxi parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Baxi fault codes
- E118Get it checkedLow water pressure on the digital-display Baxis: 600, 800, Duo-tec 2, Compact, Assure, Megaflo. Defined by Baxi as primary pressure under 0.5 bar. Repressurise and it clears itself.Related: water pressure
- E119Get it checkedLow water pressure on the selector-switch Baxis — Duo-tec Combi HE, Platinum, Megaflo System HE A. Shown as E1 then 19. Repressurise; no reset is needed.Related: water pressure
- E.02.07Usually simple to fixLow water pressure made permanent on the Baxi 200/400 Combi and Combi 2, after A.02.06 or H.02.06 has been showing. Repressurise to 1 to 1.5 bar and reset; Baxi say you can do it yourself.Related: water pressure
- E117Get it checkedPrimary water pressure too high, on the Duo-tec 2 and EcoBlue Advance. Usually an overfilled system or a flat expansion vessel. Let some water out and it clears.Related: water pressure
- E133Get it checkedBaxi's ignition lockout: "the gas supply has been interrupted, ignition has failed or the flame has not been detected". Check the gas is on, reset once. If it returns, stop.Related: same brand
- E.04.10Get it checkedIgnition failure on the Baxi 200/400 Combi and every Combi 2: the burner would not light after its allowed attempts. Baxi's own quick guide names it the frozen-condensate code you can fix yourself.Related: same brand
Own a Baxi boiler? Save it and its codes come first next time.
Related guides
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer support portal
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.