If your Ideal Logic, Logic+, Logic Max, Vogue MAX, Independent or Mexico is locked out with F3 on the display (usually with a solid red light), your heating and hot water are off and the boiler is telling you one thing loud and clear: the fan isn’t doing its job properly.
F3 means “Fan unable to reach required speed or feedback fault”.
The boiler measures fan speed constantly, and if it’s more than 400–500 rpm below target – or the speed signal disappears completely – it shuts down for safety.
This is one of the most common winter call-outs on Ideal boilers across the UK, especially on boilers 7–12 years old.
What Actually Causes F3 on Ideal Boilers
Blocked Venturi (Spider Webs and Dust)
The tiny plastic throat inside the fan gets clogged – the fan spins furiously but can’t pull enough air. This is the number-one cause on Logic and Vogue models.
Fan Motor Bearings Worn or Seizing
After 8–12 years the bearings dry out and the fan struggles, especially on cold start-up.
Water or Condensate in the Fan or APS Tubes
Rain blowing in a poorly pitched flue or a leaking sump lets water run into the clear plastic air-pressure tubes or directly onto the fan.
Faulty Air Pressure Switch (APS)
The switch doesn’t close properly even though the fan is running.
PCB Not Reading Fan Speed Correctly
Dry joint or hall-sensor failure on the board (less common than people think).
Safe DIY Checks You Can Do Right Now
Reset the boiler (hold the reset button or spanner symbol for 5 seconds) – sometimes a temporary blockage clears itself.
Go outside and safely clear leaves, snow, ice or debris from the flue terminal (ground level only).
Check the clear plastic tube from the fan to the APS isn’t kinked or full of water.
That’s it – anything else involves opening the combustion chamber and is illegal for homeowners.
When You Must Call a Gas Safe Engineer (Almost Always with F3)
F3 nearly always needs a proper strip-down and test. Only a registered engineer can:
- Remove and clean or replace the fan and venturi
- Test and replace the air pressure switch
- Check flue pitch and seals
- Carry out combustion analysis after repair
Always confirm they’re Gas Safe registered at www.gassaferegister.co.uk.
Typical 2025 Repair Costs for Ideal F3
- Venturi clean + fan service: £160–£240
- New fan assembly (most common fix): £280–£420 fitted
- New air pressure switch: £140–£200
- Full fan + venturi + APS kit: £380–£520
- New PCB (rare): £400–£580
Many Ideal engineers now quote a fixed “F3 fan fault” price because they do so many.
How to Prevent F3 Coming Back
Annual service – the engineer cleans the venturi and checks fan bearings every year.
Keep bushes trimmed back from the flue terminal.
Fit a plume management kit if the flue is in a windy spot or points at a wall.
Frequently Asked Questions About Ideal F3
What’s the difference between F3 and L3?
F3 is the current code on Logic+, Vogue and Max boilers. L3 was the old code on the original Logic and Isar/Istor – same fault, different naming.
Will resetting fix F3 permanently?
Only if it was a one-off blockage. If it returns within minutes, the fan or venturi is failing.
Is F3 covered by my Ideal warranty?
Yes – if the boiler is still within its 7–12 year warranty and has a full annual service history by an Ideal-approved installer.
My boiler is only 6 years old – why F3 already?
Usually a blocked venturi (spiders and dust) or water in the APS tubes – still fully under warranty.
F3 or F6 – which is it?
F3 = fan speed wrong. F6 = air pressure switch fault (sometimes related, but different parts).
Stay warm,
The Boilers2Go Team
With years of experience in boilers and home improvements in general, Myles Robinson is a passionate advocate for making home heating simpler, safer, and more affordable for households across the UK. With years of experience in the heating industry, Myles combines hands-on knowledge with a focus on customer-first service, helping homeowners choose the right boiler, understand their systems, and keep their heating running efficiently all year round. His articles break down complex topics into clear, practical advice you can trust.