Ideal Logic and Logic+ fault codes

An Ideal Logic or Logic+ boiler shows a fault as a short code on the front display, usually a letter followed by a number, sometimes with a lock symbol if the boiler has gone into lockout. The code itself is only half the story. The same letter and number can point to a different part depending on which Logic variant you have and when it was built, so the first job is working out exactly what boiler is in front of you before you order anything.

Finding the model range

The model name is printed on the boiler's data badge, usually inside the front casing or on a label near the bottom edge. Ideal's Logic range covers several families, including Logic, Logic+ and Logic Max, each sold as a combi, system or heat-only variant. These are not interchangeable for parts purposes. A Logic+ combi and a Logic Max combi can display the same fault code for entirely different reasons, because the boards, sensors and control logic changed between ranges.

Finding the serial number

The serial number sits on the same data badge as the model name, typically as a long numeric string. It matters here because Ideal revised components and wiring within a single model range over its production life, and a part number correct for an early Logic+ can be wrong for a later one. Where a fault code page or parts listing asks for a serial range, checking the badge against it before ordering saves a return.

Finding the firmware version

Some Logic and Logic+ boards display a firmware or software version briefly on power-up, or through a service menu accessed via the front controls. Not every fault code behaves identically across firmware revisions, particularly where Ideal updated the control logic to change how a sensor fault is reported. If a code doesn't match the description given for your model, an older or newer firmware version is worth checking before assuming the code has been misread.

Before you go further

• Note the exact code shown, including any letter suffix
• Record the model name from the data badge
• Record the serial number from the data badge
• Check for a firmware version on power-up or in the service menu, if your model shows one

With those four details to hand, a fault code can be matched to the right component and the right part number. Some replacements are straightforward for a competent homeowner; others involve gas-carrying components and must be carried out by a Gas Safe registered engineer. For the rules on which is which, see the Gas Safe rules for boiler repairs guide. If your boiler is a different make, the fault code tables and part numbers won't apply, so check the guide for your specific brand on the boiler brands page instead.

F1 is the ignition lockout code on an Ideal Logic boiler, and it's usually the first fault code an owner ever sees. It means the boiler tried to light the burner, did not detect a flame within the time it allows, and shut itself down.

What's actually going wrong

A lockout on ignition can come from several places along the same chain: gas reaching the burner, a spark forming to light it, and the flame being sensed once it's lit. If any one of those steps fails, the boiler reads it as a failed ignition attempt and locks out after the permitted number of tries.

Components worth checking

• Gas supply - a closed valve elsewhere in the house, or a meter that's tripped, will produce the same code as a faulty part inside the boiler.
• Ignition electrode - the spark gap can close up or carbon over with age, weakening the spark that lights the gas.
• Flame sensor (NTC sensor) - if the boiler can't confirm the flame is burning once lit, it treats the attempt as failed even when ignition actually occurred.
• Gas valve - a valve that isn't opening fully will starve the burner of gas at the moment of ignition.
• Printed circuit board (PCB) - less common, but a fault here can misread a healthy flame signal as absent.

The most common cause on an Ideal Logic is a worn or misaligned ignition electrode, but that's a statement about frequency, not a diagnosis for any one boiler.

Why the part number depends on the model

The Logic and Logic+ ranges have gone through several revisions, and the electrode, flame sensor and PCB fitted to an early Logic combi are not always interchangeable with a later Logic+ model. Checking the model range and serial number against the fault code reference table elsewhere in this guide, and against the label on the part itself, is the way to confirm which part number applies before ordering anything.

What you can do yourself

Checking that the gas supply is on, the boiler has power, and nothing else in the house has tripped is fine for anyone to do. Opening the casing to inspect or replace the ignition electrode, gas valve or flame sensor is not. This work must be carried out by a Gas Safe registered engineer. The Gas Safe rules for boiler repairs guide sets out where that line sits in more detail, and if the PCB turns out to be the fault, the PCB replacement guide covers identifying and sourcing the right board.

Fault code F2 means the boiler tried to light and either failed to detect a flame or lost the flame signal after ignition. That is a different failure point to F1, which is a straightforward ignition lockout where the burner never lit at all. F2 usually means the burner did light, at least briefly, but the boiler could not confirm it was still burning and shut down as a safety response.

How the flame sensor fits in

The flame sensor (sometimes called the flame rectification probe) sits in the combustion chamber next to the burner. Once the boiler ignites, it uses this probe to check for a genuine flame signal, and it keeps checking for as long as the burner is firing. If the signal drops out, weakens, or was never clean to begin with, the printed circuit board (PCB) reads that as flame loss and stops the boiler.

A weak or dirty flame sensor is the most common reason for F2. Carbon deposits on the probe tip, poor earthing, or a probe positioned slightly out of the flame can all produce a signal too weak for the PCB to trust, even though the burner is actually alight.

What else can trigger F2

• A flame sensor that is fouled, corroded, or has drifted out of position
• Poor gas pressure or an unstable flame at the burner, which gives the sensor nothing reliable to read
• A faulty gas valve that is not delivering a consistent flame
• Wiring or an earthing fault between the sensor and the PCB
• A PCB that is misreading a perfectly good flame signal

That last point is the one worth taking seriously before reaching for a new circuit board. A PCB fault is the least common cause of F2, and it should be considered only once the flame sensor, its wiring, and the gas supply to the burner have been checked and ruled out.

When a PCB replacement is indicated

Replacing the PCB is indicated when a known-good flame sensor still produces an unstable or absent signal at the board, or when the board fails to respond correctly to a signal that testing confirms is present and clean. Combustion and gas valve components sit behind this fault, so diagnosing it properly means working on gas-carrying parts. This work must be carried out by a Gas Safe registered engineer.

For the part numbers behind F2 and the model ranges they apply to, see the fault code reference table on this page. If you are unsure whether the work in front of you falls inside or outside DIY territory, the rules are set out in full in our Gas Safe rules for boiler repairs guide.