Fujitsu serial communication error (E1:00 / code 11)

What this error means

The indoor and outdoor units stopped talking — Fujitsu's version of the fault every mini-split brand shares (Mitsubishi E6, Daikin U4, LG CH05, Panasonic H11). Wiring, power to one unit, or a board. The breaker reset clears transient cases; recurrence is a technician diagnosis.

Symptoms

• Unit stops; EE:EE→E1:00 or code 11
• After power events

Try this first (safe DIY steps)

1. Kill power at the breaker/disconnect 3–5 minutes; restore
2. Confirm the outdoor unit has power
3. Log recurrence timing

Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.

When to call a technician

Inter-unit wiring and PCB work — service.