UA-66 High

Daikin UA-66 Fault Code

Also written as UA66 — same fault.

The Daikin UA-66 fault code means: your boiler's internal memory chips are having trouble communicating with each other, meaning the control board doesn't recognise the boiler's specific settings.. It appears on 1 Daikin model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Boiler chip card ID (BCC-iD) of internal Electrically Erasable Programmable Read-Only Memory (EEPROM) is inconsistent

What causes the Daikin UA-66 fault?

This fault occurs when the boiler's main control board loses its connection to the memory chip that holds the unit's unique identity and configuration settings. The most common reason is a physical failure of the chip itself or electrical interference that has corrupted the data exchange between internal components.

Typical repair cost £180-450 (including labour)

Engineer required

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

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Daikin models that show the UA-66 fault code

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

Source

Daikin UA-66 fault code information on this page is sourced and cross-checked against the official Daikin service / installation manuals for each affected model.

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