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AC-00

AC-00 — Booster heater overheated

Daikin · ASHP Error Codes

What does AC-00 mean?

The booster heater within the system has overheated.

Common Causes

  • Thermostat failure
  • Overheating due to restricted flow
  • Faulty heating element

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Ensure water flow to the booster heater is not obstructed.

  2. 2

    Check the booster heater's temperature settings.

  3. 3

    Perform a system reset by cycling the power.

  4. 4

    A service professional needs to diagnose the booster heater.

Browse all codes in this manual (60)
Verified technical data. Last updated: April 2026

Related Faults

7H-017H-01 — Water flow problem7H-047H-04 — Water flow problem during domestic hot water production7H-057H-05 — Water flow problem during heating/sampling
Source: Daikin ASHP Error Codes
Open Manual (Page 2)Search more codes in this manual