Error code
13 Serial communication fault (forward transfer)
How it shows on the unit OPERATION lamp (green) off, TIMER lamp (orange) 4 or 5 blinks (each flash 0.5 s on / 0.5 s off), COIL DRY lamp off
Applies to 4 models
What this means
The outdoor unit receives no signal from the indoor unit (serial forward-transfer 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 Fujitsu manual (hosted by an authorized distributor)Hosted by an authorized distributor rather than by the manufacturer. We link to manuals, we never host them.
Using Claude Code or Meta Muse? Connect HeatPump AI and ask it about 13.