Error code
P4 Inverter heat-sink temperature-sensor fault
Applies to 6 models
FTXS35K2V1B, FTXS42K2V1B, FTXS50K2V1B, FTXS35K3V1B, FTXS42K3V1B, FTXS50K3V1B
What this means
The inverter-circuit heat-sink temperature sensor has malfunctioned.
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.
Using Claude Code or Meta Muse? Connect HeatPump AI and ask it about P4.