H.03-.02 Boiler Fault Code: What It Means on Every Brand

The H.03-.02 fault code appears on 2 boiler brands — Baxi and Remeha — 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.

Engineer may be needed 2 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 H.03-.02 means	Severity	DIY?
BBaxi	The H.03-.02 is a temporary (H-type) blocking fault on Baxi boilers, indicating that the flame supervision circuit failed to detect or maintain an ionisation current during operation. Full guide →	Engineer may be needed	No
RRemehashown as H.03.02	The H.03.02 code on Remeha boilers indicates a blocking fault caused by a flame signal that is too weak or completely absent. Full guide →	Engineer may be needed	No

H.03-.02 brand by brand

Baxi H.03-.02

The H.03-.02 is a temporary (H-type) blocking fault on Baxi boilers, indicating that the flame supervision circuit failed to detect or maintain an ionisation current during operation. In plain terms, the boiler either attempted to fire and could not confirm a stable flame, or the flame dropped out during normal running. As a blocking fault rather than a hard lockout, the boiler may attempt to recover automatically once the underlying condition clears — but if the problem persists or repeats, manual intervention is needed. The root cause typically lies somewhere in the ignition and flame-sensing chain: the ionisation electrode, gas supply, ignition leads, gas valve, or flue system.

Causes, fixes & costs for Baxi H.03-.02 → · All Baxi codes

Remeha H.03.02

The H.03.02 code on Remeha boilers indicates a blocking fault caused by a flame signal that is too weak or completely absent. In practical terms, the boiler attempted to fire but either failed to establish a flame or lost it during operation — and the ionisation electrode, which monitors the flame, reported no usable signal back to the PCB. As a safety precaution the boiler immediately closed the gas valve and stopped. Unlike an 'E' prefix lockout code, the 'H' prefix means this is a temporary blocking fault that may clear with a reset once the underlying cause is resolved. Remeha models that commonly display this code include the Tzerra Ace, Calenta, and Quinta ranges.

Causes, fixes & costs for Remeha H.03.02 → · All Remeha codes

Frequently asked questions

Is the H.03-.02 fault code the same on every boiler?

Broadly, yes — on Baxi and Remeha the H.03-.02 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 H.03-.02 fault myself?

Not usually. On every brand listed, H.03-.02 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a H.03-.02 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.