Ideal Boiler FD Fault Code Cause & Fix

If your Ideal boiler is flashing FD (sometimes alternating with a red flashing light or showing “Fd” on the screen), your heating has just ground to a halt. Whether you’ve got a Logic+, Logic Max, Vogue MAX, Independent, or an older Isar/Istor, the FD fault is Ideal’s way of shouting “FLAME DETECTION LOCKOUT!”

In plain English: the boiler tried to light but couldn’t prove a proper flame was established or staying lit.

This is one of the most common winter call-outs for Ideal boilers in British homes – from Edinburgh tenements to new-build semis in the Midlands and flats in London. The good news? Sometimes it’s a 30-second fix. The bad news? It’s almost always a gas-side issue, so you usually need a Gas Safe engineer.

What Exactly Does FD Mean on an Ideal Boiler?

FD = Flame Detection Fault (sometimes shown as Fd or just a permanent red light on older models).

The boiler has opened the gas valve, sparked the electrodes, but the flame rectification probe didn’t send the correct signal back to the PCB within the allowed time (usually about 7–10 seconds). The boiler then locks out for safety.

The Real-World Causes We See Every Day in UK Homes

1. Condensation dripping onto the PCB or electrodes Very common on Logic and Vogue boilers over 6–7 years old – the condensate trap or siphon leaks a few drops straight onto the board or ignition box.
2. Cracked ignition or flame-sensing electrode The ceramic cracks and the probe gives false readings (costs about £130 to replace).
3. Gas valve sticking or out of calibration The solenoid doesn’t open fully or drifts over time – classic on boilers 8+ years old.
4. Moisture in the air intake or flue Heavy rain blowing into a horizontal flue, or a blocked or iced-up vertical flue terminal.
5. PCB fault The printed circuit board misreads the flame signal (expensive, but less common than people think).
6. Very low or fluctuating gas pressure Especially on cold mornings when the whole street fires up at once.
7. Blocked burner or injectors Usually only after years without a proper service.

Note: FD is NOT the same as L2 (old Ideal code) or F1 (low pressure) or F2 (flame loss after lighting). FD specifically means the boiler never saw a flame in the first place.

Safe DIY Checks You Can Do Right Now

These are the only things you’re legally allowed to try:

1. Press and hold the reset button for 5 seconds (On Logic+ it’s the spanner symbol; on Vogue it’s the flame reset button). If it fires and stays on – brilliant, it was just a temporary glitch. If FD comes straight back, stop.
2. Check your gas supply Is the meter emergency control valve fully open (handle in line with the pipe)?
3. Look outside at the flue terminal Clear any leaves, snow, ice or wasp nests (only if safe from ground level).
4. Check for obvious leaks underneath the boiler A puddle or dripping condensate trap often causes FD on Ideal boilers.

That’s it. Anything else involves removing the combustion cover and is strictly Gas Safe territory.

When You Absolutely MUST Call a Gas Safe Engineer

FD is 99% of the time a gas or ignition component fault. By law and for your safety, only a registered engineer can:

• Test and adjust the gas valve
• Replace electrodes or leads
• Dry out or replace a wet PCB
• Carry out a full combustion analysis after repair

Check they’re genuinely registered at www.gassaferegister.co.uk

Typical 2025 Repair Costs for FD Fault

• New electrode pack + clean: £130–£190 fixed price
• Gas valve recalibration or replacement: £280–£420
• Condensate trap/siphon replacement: £140–£200
• New main PCB (worst case): £380–£580 fitted

Many engineers now quote fixed-price “Ideal FD repairs” because they see it so often.

How to Prevent FD Happening Again

• Annual service – the engineer cleans the sump and checks for early condensate leaks
• Fit an in-line condensate pump or pro kit if your boiler is in a loft
• Install a good magnetic filter (Ideal or MagnaClean)
• If your boiler is 10+ years old and getting repeat FD faults, start budgeting for a new Logic Max or Vogue MAX – parts are getting harder to source for the very old Isar/Istor HE models.

Frequently Asked Questions About Ideal FD Fault

Will resetting fix FD permanently?

Only if it was a one-off glitch. If it keeps returning, there’s a real fault.

Is FD covered by Ideal warranty?

Only if the boiler is still in its 7–12 year warranty AND has a full service history.

Why does FD happen after heavy rain?

Water runs down the flue and into the electrodes or air pressure switch area.

My boiler is only 4 years old – why FD already?

Usually a cracked electrode or early condensate leak – still warranty if serviced every year.

FD or F1 – which is worse?

F1 is low pressure (DIY fix). FD is flame detection (engineer only).

Staring at FD right now? Drop your exact model (Logic+ 30, Vogue MAX 32, Independent C30 etc.) in the comments and we’ll tell you the most likely cause and rough cost.

Stay warm,

The Boilers2Go Team