81-65 Low

Daikin 81-65 Fault Code

Also written as 8165 — same fault.

The Daikin 81-65 fault code means: your boiler is still providing heating and hot water, but it has detected a problem with the temperature sensor for your solar thermal system.. It appears on 1 Daikin model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Domestic hot water (DHW) temperature sensor error. The boiler will continue in operation but solar sensor has an error

What causes the Daikin 81-65 fault?

This fault occurs when the boiler loses communication with the temperature sensor attached to your solar thermal panels. The most common reason is a physical break in the sensor's wiring or the sensor itself failing due to the extreme temperature fluctuations it experiences on the roof.

This fault is more common during the summer months when solar thermal systems are under peak thermal stress and high operating temperatures.

Typical repair cost £90-180 (including labour)

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Daikin models that show the 81-65 fault code

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

Source

Daikin 81-65 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