BoilerFaultCodesIdeal J43 Fault Code
The Ideal J43 fault code means: your heat pump's internal control board has detected a communication or electrical fault with the motor that drives the system, meaning it cannot currently provide heating.. It appears on 1 Ideal model in our database.
Technical description: Inverter Error
What causes the Ideal J43 fault?
This fault occurs when the main control board loses the ability to communicate with or power the motor that drives the heat pump. It is usually caused by a failure in the electrical components that manage the compressor's speed, or a physical electrical fault within the compressor itself. When this happens, the system cannot safely move heat into your home and will shut down to prevent further damage.
This fault is more frequent during extreme cold spells when the system is working at its maximum capacity to maintain indoor temperatures.
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 J43 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal J43 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