6 High

Unical 6 Fault Code

The Unical 6 fault code means: your boiler has shut down because it has detected it is getting too hot, likely due to a lack of water flow through the system.. It appears on 2 Unical models 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: HIGH TEMPERATURE Boiler temperature too high
Typical repair cost £120-350 (including labour)

DIY fix possible

Check that all radiator valves are fully openEnsure the boiler pressure gauge is between 1.0 and 1.5 barPress the reset button to see if the fault clears after the system cools down

Find a Gas Safe engineer

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

Gas Safe Register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like 6: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Unical models that show the 6 fault code

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

Source

Unical 6 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 7 July 2026