Error code
C4 Indoor heat-exchanger thermistor fault
Applies to 24 models
CTXA15A2V1BW, FTXA20A2V1BW, FTXA25A2V1BW, FTXA35A2V1BW, FTXA42A2V1BW, FTXA50A2V1BW, CTXA15(A)(B)2V1BS, FTXA20(A)(B)2V1BS, FTXA25(A)(B)2V1BS, FTXA35(A)(B)2V1BS, FTXA42(A)(B)2V1BS, FTXA50(A)(B)2V1BS, CTXA15(A)(B)2V1BT, FTXA20(A)(B)2V1BT, FTXA25(A)(B)2V1BT, FTXA35(A)(B)2V1BT, FTXA42(A)(B)2V1BT, FTXA50(A)(B)2V1BT, CTXA15B2V1BB, FTXA20B2V1BB, FTXA25B2V1BB, FTXA35B2V1BB, FTXA42B2V1BB, FTXA50B2V1BB
What this means
The indoor heat-exchanger temperature sensor has a fault.
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.
See the official Daikin manualA deep link to the manufacturer's own PDF for full technical detail. We link to manuals, we never host them.
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