How much does it cost to fix Baxi error code L3?

Typical repair cost for the Baxi L3 fault is £120-220 including labour.

L3 High

Baxi L3 Fault Code

Q: What does the Baxi L3 fault code mean?

Your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has purposefully shut down to prevent damage.

The Baxi L3 fault code means: your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has purposefully shut down to prevent damage.. It appears on 1 Baxi model in our database.

Technical description: Thermistor Fault (Return)

Typical repair cost £120-220 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Baxi models that show the L3 fault code

Click a model for the full fault code list and model-specific repair notes.

130 HE (range) Repair: £120-220

Source

Baxi L3 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026