F6 Low

Ideal F6 Fault Code

The Ideal F6 fault code means: your boiler has lost connection with the sensor that monitors the outdoor temperature, making it difficult for the system to adjust its heat settings efficiently.. It appears on 17 Ideal models 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: Outside Sensor Fault

What causes the Ideal F6 fault?

This fault occurs when the boiler's main control board can no longer communicate with the external sensor mounted on the outside of your home. The most common reason is damage to the thin communication wires by pests or garden maintenance, or water entering the sensor housing and causing corrosion. Because the boiler no longer knows how cold it is outside, it cannot automatically adjust its temperature to save you money on your energy bills.

This fault is often noticed during autumn or the first cold snap, as this is when the boiler starts relying on the outdoor sensor to ramp up the heating demand.

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 →

Ideal models that show the F6 fault code

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

Source

Ideal F6 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.

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