13 Medium

Unical 13 Fault Code

The Unical 13 fault code means: your boiler is having trouble reading the temperature of your hot water supply due to a faulty sensor or loose wiring.. It appears on 2 Unical models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: DOMESTIC HOT WATER SENSOR Domestic hot water sensor fault (1). Check the efficiency of the sensor (see table Res/Temp) (Par.4) or its connections.
Typical repair cost £90-180 (including labour)

Engineer required

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

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Unical models that show the 13 fault code

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

Source

Unical 13 fault code information on this page is sourced and cross-checked against the official Unical service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026