E128 Boiler Fault Code: What It Means on Every Brand

The E128 fault code appears on 3 boiler brands — Baxi, Main and Potterton — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 3 brands use this code

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What E128 means	Severity	DIY?
BBaxi	The E128 code appears on Baxi boilers when the appliance has tried to light the burner multiple times — up to 12 ignition attempts — but has been unable to sustain a stable flame. Full guide →	Lockout — engineer likely	Some checks
MMain	The E128 fault code on Main boilers signals a repeated flame failure lockout. Full guide →	Lockout — engineer likely	No
PPotterton	The E128 code appears on Potterton boilers when the appliance has lost its flame — or failed to establish one — during normal operation. Full guide →	Lockout — engineer likely	Some checks

E128 brand by brand

Baxi E128

The E128 code appears on Baxi boilers when the appliance has tried to light the burner multiple times — up to 12 ignition attempts — but has been unable to sustain a stable flame. Rather than continuing to try indefinitely, the boiler locks out as a precaution, stopping the gas supply until the underlying problem is identified and resolved. You may have noticed the boiler firing up briefly before cutting out, or it may simply display E128 without lighting at all. Common triggers include a frozen condensate pipe in cold weather, a disrupted gas supply, or a worn ignition or flame-sensing electrode — but internal faults with the burner, gas valve, or PCB can also be responsible.

Causes, fixes & costs for Baxi E128 → · All Baxi codes

Main E128

The E128 fault code on Main boilers signals a repeated flame failure lockout. The boiler monitors every ignition attempt and, after detecting 12 consecutive instances where a flame either failed to establish or was lost unexpectedly during operation, it shuts down completely and displays E128 on the panel. This behaviour is a deliberate safety mechanism — the boiler refuses to keep attempting ignition indefinitely when something is clearly preventing stable combustion. Because Main, Baxi, and Potterton boilers share the same BDR Thermea / Baxi Group control platform, E128 carries an identical meaning across all three brands. Until the underlying cause is resolved and the boiler is reset, it will remain locked out and produce no heat or hot water.

Causes, fixes & costs for Main E128 → · All Main codes

Potterton E128

The E128 code appears on Potterton boilers when the appliance has lost its flame — or failed to establish one — during normal operation. As a safety measure, the boiler will attempt to re-ignite automatically, but once it has made around 12 unsuccessful attempts it gives up and locks out, displaying E128 on the panel. The root cause is most commonly a problem with ignition components, gas supply, or a frozen condensate pipe in winter. On some Potterton models, particularly older Promax units, the fault can also reflect a PCB-level electrical failure rather than a straightforward ignition issue. Either way, the boiler will not restart safely until the underlying fault has been resolved.

Causes, fixes & costs for Potterton E128 → · All Potterton codes

Frequently asked questions

Is the E128 fault code the same on every boiler?

Broadly, yes — on Baxi, Main and Potterton the E128 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a E128 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. The underlying repair usually needs a registered engineer. Never open the boiler casing yourself.

Who should I call about a E128 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.