How much does it cost to fix Ideal error code F U?

Typical repair cost for the Ideal F U fault is £90-250 including labour.

F U High

Ideal F U Fault Code

Q: What does the Ideal F U fault code mean?

Your boiler has detected that the water is not flowing through the pipes quickly enough, causing a large temperature gap between the outgoing and incoming pipes.

Also written as FU — same fault.

The Ideal F U fault code means: your boiler has detected that the water is not flowing through the pipes quickly enough, causing a large temperature gap between the outgoing and incoming pipes.. It appears on 1 Ideal model in our database.

Technical description: Flow/Return Differential > 50°C

Typical repair cost £90-250 (including labour)

DIY fix possible

Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 bar on the gaugeCheck for any visible leaks around the radiators or pipeworkBleed all radiators to remove trapped air

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 F U: 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.

Ideal models that show the F U fault code

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

Instinct2 24 Repair: £90-250

Source

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

Ideal Instinct2 24 manual (PDF)

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026