BoilerFaultCodesIdeal L43 Fault Code
The Ideal L43 fault code means: your heat pump has stopped working because its internal computer board is having trouble communicating with the compressor system.. It appears on 1 Ideal model in our database.
Technical description: Inverter Error
What causes the Ideal L43 fault?
This fault occurs when the main control board loses its digital connection with the inverter, which is the component responsible for managing the heat pump's power. The most common reason is an internal electronic component failure or a loose connection in the wiring that prevents the system from safely starting the compressor.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the L43 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal L43 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