Baxi [E.01.04] fault codewhat it means and how to fix it

E.01.04 is a counting code. Each time the burner loses its flame while running the board shows H.03.02, "temporary flame loss", and relights; the 200/400 Combi manual defines E01 04 as "5 x flame loss in 24 hours with burner on" and the Combi 2 manual as "flame loss detected five times in 24 hours (with burner on)", the point at which the board stops trying and locks out. It is the two-part and dotted displays' equivalent of E128 on the three-digit Baxis, and like E128 it describes a burner that can light but cannot stay lit.

Baxi's engineer tables agree on what to look at. The Combi 2: "GAS SUPPLY — check the gas supply pressure, check the gas valve calibration, check the air intake and flue gas exhaust terminal, check the power supply voltage." The 200/400 adds the ionisation side: "no ionization current — purge the gas supply to remove air, check that the gas valve is fully opened, check the supply pressure, check the operation and setting of the gas valve unit, check that the air inlet and flue gas discharge flues are not blocked, check that there is no recirculation of flue gases." That last item is why this page is rated danger.

A flame that keeps failing under load is often a flame being starved or disturbed — by low gas pressure at full rate, by a flue terminal where exhaust is being drawn back into the air intake, by wind at a badly sited terminal — and those are combustion faults. The 200/400 table lists one temporary cousin worth knowing, H.03.54, flame loss caused by "the power supply voltage being too low", which the Combi 2 also prints. The reset is the RESET button — one second on a Combi 2, at least three seconds on a 200 or 400 — and it will work, because the counter clears; but the count will start again, and a boiler that reaches five in a day twice is not going to fix itself.