Ideal F9 fault codewhat it means and how to fix it
The control board has not been told what boiler it is in, or has failed. L9 is the same fault locked out. The 2011 Logic Combi row also covers a gas valve short circuit.
Take care
Get a Gas Safe registered engineer to look at your Ideal F9
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What F9 means
Ideal call this Unconfigured PCB, and the name is literal. A Logic board leaves the factory blank and has to be told, at installation or after a replacement, whether it is in a combi or a system boiler, what gas it burns and what output size it is.
Until that is done it shows F9, and Ideal's ESP1 manual documents the sequence a new board goes through — uP on power-up, oF after Restart, then F9 until the installer dials in C for combi, n for natural gas and the boiler size with the central heating knob, pressing Restart after each. The manual puts in capitals that setting the correct size is critical for safe operation, because the board uses it to decide how hard to drive the fan and gas valve.
So F9 on a boiler that has just had work done means somebody did not finish the job; F9 on a boiler nobody has touched means the board has lost its configuration or failed. The 2011 Logic Combi guide widens the row to "unconfigured/faulty PCB or gas valve short circuit", and the Combi2 simply says PCB Fault, replace PCB.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| New PCB fitted and not programmed | The most common route to F9 by far. The replacement board is working perfectly; it has not yet been told the type, gas and size, and will not run until it has. | Common |
| Board has lost its stored configuration | A brown-out or a board fault can wipe the settings. The boiler was fine yesterday and shows F9 today with nothing else changed. | Occasional |
| PCB failure | Where configuration does not hold or cannot be entered, Ideal's chart ends at replacing the board. | Occasional |
| Gas valve coil shorted | On the 2011 Logic Combi, Ideal include a gas valve short circuit in this row. The board sees a load it cannot make sense of and reports itself faulty. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£60–£380
Time on site
1 hour
Configuring a board that was left unprogrammed is a short visit, £60–£90. A replacement primary PCB fitted and configured is £250–£380.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Ideal Logic primary PCB
£150–£320Authorised Ideal parts distributor
Price checked 28 September 2026
Ideal Logic gas valve
£90–£200Authorised Ideal parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Ideal fault codes
- dUUsually simple to fixNot a fault. The diverter valve has been parked in its mid-position for servicing and the boiler is waiting to be told the service is over. Ideal publish the way out.Related: electronics and power
- Blank displayGet it checkedNothing on the screen at all. Ideal's user guides send you to the boiler's switch and the consumer unit first; the installer charts then work from the terminal block to the board.Related: electronics and power
- F7Get it checkedThe mains voltage reaching the boiler has dropped below what the board will run on. Ideal's advice is an electrician or your electricity supplier, not a heating engineer.Related: electronics and power
- C0Get it checkedThe board cannot activate the Boiler Chip Card that tells it what model it is fitted to. Ideal's engineer check is whether the small plastic card is in its slot at all.Related: electronics and power
- L9Get it checkedOn a Logic, L9 is the locked-out form of the unconfigured-board fault F9. On an Isar HE it is something else entirely: a heat exchanger overheat read by the dry-fire thermistor.Related: electronics and power
- SEUsually simple to fixA service reminder, not a fault. The installer set a timer at the last visit and it has run down. Ideal's advice is to contact the installer, who resets it when the boiler is serviced.Related: electronics and power
Own an Ideal boiler? Save it and its codes come first next time.
Related guides
Common questions about Ideal F9
Can I configure the board myself if the instructions are in the manual?
No. Ideal print the sequence in the installation manual, not the user guide, and they say in capitals that the size setting is critical to safe operation. Telling a 24 kW board it is a 35 kW boiler makes it run the gas valve for a burner it does not have. This is Gas Safe work.
Which Ideal boilers show F9?
Every Logic generation, the Independent, the i-mini and the Logic Code Combi. The ESP1 groups it as "F9 or L9 or F8 or L8 — PCB unconfigured or faulty". Logic+, Logic Max and Vogue show PCB Fault or Unconfigured PCB in words. On an old Isar or Icos, a board fault is L E or H E instead, and L9 there means an overheat, not a board.
The boiler was just serviced and now shows F9. Is that connected?
Very likely. If the PCB was changed during the visit and the configuration was not completed, or was entered wrongly, this is the code you get. Ring the engineer who did the work before paying anyone else.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.