Error code
C4 Heat-exchanger temperature sensor fault
Applies to 15 models
FTXJ20A2V1BW, FTXJ25A2V1BW, FTXJ35A2V1BW, FTXJ42A2V1BW, FTXJ50A2V1BW, FTXJ20A2V1BS, FTXJ25A2V1BS, FTXJ35A2V1BS, FTXJ42A2V1BS, FTXJ50A2V1BS, FTXJ20A2V1BB, FTXJ25A2V1BB, FTXJ35A2V1BB, FTXJ42A2V1BB, FTXJ50A2V1BB
What this means
The heat-exchanger temperature sensor has a problem.
When to call a technician
This fault involves refrigerant, pressure, or electrical work that must be handled by a certified technician under EU F-gas rules. Do not attempt to open the refrigerant circuit, access mains wiring, or adjust pressure components yourself. Contact a qualified installer or servicer for this one.