BoilerFaultCodesIdeal L9 Fault Code
The Ideal L9 fault code means: your boiler's internal computer has forgotten its settings or has developed a technical communication error, meaning it cannot safely control the heating process.. It appears on 16 Ideal models in our database.
Technical description: Printed circuit board (PCB) unconfigured or fault
What causes the Ideal L9 fault?
This fault occurs when the boiler's central control board loses its identity or suffers a data communication failure, preventing it from managing the gas valve and pumps. The most common reason is a hardware failure within the motherboard or a missing configuration chip, which acts like a memory card telling the boiler exactly which model it is. It can also be triggered by a sudden power surge or electrical interference that corrupts the board's stored settings.
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 L9 fault code
Click a model for the full fault code list and model-specific repair notes.
- Esprit HE Repair: £100-350
- Icos Repair: £120-250
- Icos HE Repair: £150-300
- Icos System Repair: £120-350
- Isar HE Repair: £150-350
- Isar System Repair: £150-350
- Logic Code Combi ESP1 Repair: £280-450
- Logic Combi C24 C30 C35 Repair: £250-£550
- Logic Combi ESP1 Repair: £280-450
- Logic Max & Logic Plus Repair: £250-£450
- Logic Max Combi Repair: £280-450
- Logic Max Plus Repair: £250-£450
- Logic Max System Repair: £280-450
- Logic+ System Repair: £280-450
- Mexico HE Repair: £150-£450
- Mexico Super 100FF / 125FF Repair: £150-300
Source
Ideal L9 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