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11

Error 11 (1 Green, 1 Red Flash) — Communication error between Hydraulic and Outdoor unit

Fujitsu · Air to Water Heat Pumps

What does 11 mean?

The hydraulic unit's green LED flashes once and the red LED flashes once, indicating a problem with communication between the indoor hydraulic unit and the outdoor unit. This means the two main parts of your heat pump system are not communicating properly.

Common Causes

  • Incorrect wiring or loose connections between the hydraulic and outdoor units.
  • External interference, such as electromagnetic waves.
  • A fault with the outdoor unit's main PCB.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Stop the heat pump system by disconnecting power, wait at least one minute, then restart the system.

  2. 2

    Check all electrical connections between the hydraulic unit and the outdoor unit, ensuring they are secure and correctly wired.

  3. 3

    Inspect the area for any equipment generating strong electromagnetic waves that might be interfering with the system's communication.

  4. 4

    Verify the power supply voltage to the outdoor unit is between AC 198-264 V at terminals N and L. Consult a qualified technician for voltage checks.

  5. 5

    Check the serial signal voltage between terminals 2 and 3 of the outdoor terminal block; it should fluctuate between AC 70 V and AC 130 V. If not, the Main PCB may need replacement by a professional.

Browse all codes in this manual (59)
Verified technical data. Last updated: April 2026

Related Faults

1 Flash (Outdoor Unit)Outdoor Unit LED 1 Flash — Serial forward transfer error10Fault 10 — Outdoor sensor error11 Flashes (Outdoor Unit)Outdoor Unit LED 11 Flashes — Discharge temperature error (permanent stoppage)
Source: Fujitsu Air to Water Heat Pumps
Open Manual (Page 10)Search more codes in this manual