Quick Answer

  • Test points: Terminal 2 (Neutral) to Terminal 3 (Signal)

  • Expected indoor values (Terminal 2–3):

    • AST & ART/C: 60–120 V

    • ASTA & ASTB: 40–90 V

    • ASTG: ~200 V (static)

    • ARTG & 3-phase: ~295 V (static)

    • ARTH: 50–250 V

  • Expected outdoor values (Terminal 2–3):

    • AOTA: 60–120 V

    • AOTG: 3–110 V

    • AOTH: 3–110 V

What is it?

A voltage test that confirms the DC serial communication signal exists between indoor and outdoor.

Tools

  • Digital Multi Meter(AC/DC voltage)

Procedure

  1. Disconnect the signal wire

  2. Measure voltage between Terminal 2 (N) and Terminal 3 (Signal) at the indoor terminal block.

  3. Measure the same at the outdoor terminal block.

  4. Record whether voltage is stable, fluctuating, or absent.




Pass Criteria

  • Voltage is within the applicable range listed above.

If it fails (Solution)

  • Indoor has signal, outdoor does not:
    Action: Inspect/repair signal wiring and terminations; proceed to DC bus and supply rail checks to rule out outdoor PCB resets.

  • Neither end has signal:
    Action: Treat as wiring/termination issue first; confirm correct terminals and replace/repair interconnect if damaged.

  • Signal unstable/intermittent:
    Action: Treat as possible PCB reset or rail collapse; isolate loads using staged reconnect (see “Staged Reconnect Test”).