Serial communication error: the indoor unit is not receiving the serial signal from the outdoor unit. The operation lamp blinks once and the timer lamp blinks once.
Fujitsu 11 on ASUG09/12/15LZAS is a serial communication error. The operation lamp blinks once and the timer lamp blinks once, and the economy lamp flashes continuously. Code 41 blinks 4 and then 1 and is the room temperature sensor. The service manual's first check for 11 is a power reset. If the blink returns, the wiring and the outdoor board are technician work.
Likely causes
- Connection failure between the indoor and outdoor units
- External electrical noise
- Outdoor unit main PCB failure
- Outdoor unit fan motor failure
Safe checks for 11
- Switch the breaker off, wait a minute, and turn it back on. If the same 1-and-1 blink returns, stop
- Technicianthe manual then checks the indoor-to-outdoor connections and the power supply at the outdoor unit
Capacitors can hold a charge after the power is off. Safety terms.
When to call a pro
A repeating 1-and-1 blink is wiring, noise, the outdoor fan motor, or the outdoor main board. Do not measure the outdoor terminals. Call a licensed HVAC technician.
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