How much does it cost to fix Alpha error code 73?

Typical repair cost for the Alpha 73 fault is £150-250 including labour.

73 High

Alpha 73 Fault Code

Q: What does the Alpha 73 fault code mean?

Your boiler has detected an inconsistent temperature reading between two of its internal safety sensors, causing it to shut down to prevent overheating.

The Alpha 73 fault code means: your boiler has detected an inconsistent temperature reading between two of its internal safety sensors, causing it to shut down to prevent overheating.. It appears on 10 Alpha models in our database.

Technical description: High flow NTC and safety NTC difference detected. The board detects an anomaly in the temperature readings difference between the flow NTC and safety NTC sensors

Typical repair cost £150-250 (including labour)

Engineer required

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

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Alpha models that show the 73 fault code

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

Source

Alpha 73 fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.

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