Purpose

This document provides a structured overview of diagnostic test procedures for key components within Fujitsu inverter and standard air conditioning systems. It serves as a quick reference guide for technicians performing on-site electrical testing, fault isolation, and verification of component functionality.

Contents Overview

The guide outlines power-off and power-on test methods for critical system components, covering:

  1. Signal Communication Tests

    • System signal verification between indoor and outdoor units.

    • 3-wire remote controller signal test (Y1, Y2, Y3 terminals).

    • DC serial communication expected voltage values for both indoor and outdoor circuits

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  2. Power Conversion & Drive Components

    • Diode Bridge (1-Phase / 3-Phase): Converts AC supply to DC voltage.

      • Expected readings: 0.4 V forward voltage drop per diode; 0.7–0.9 V between + and –

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    • Active Filter Module (ACTPM): Improves power factor and supplies DC bus to inverter.

      • Resistance test range: 360 kΩ – 900 kΩ between terminals

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    • Intelligent Power Module (IPM): Drives compressor windings (U, V, W).

      • Expected diode readings: 0.4 V ± 0.1 V per phase

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  3. Fan Motor Testing

    • DC Brushless Motors: Operate at 330–380 V DC (main power) and 15 V DC (control).

      • Verify diode readings: 0.5 – 1.8 V (white-to-black), 0.8 – 1.1 V (black-to-red)

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    • AC Fan Motors: Check resistance across phases; refer to fan-specific tables (typically 5–20 Ω range).

  4. Sensor Testing

    • Thermistors:

      • Power-on: Expect 5 V DC supply with a lower return voltage (temperature-dependent).

      • Power-off: Cross-check resistance values using thermistor tables or the Mobile Technician App

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    • Pressure Transducer:

      • 5 V DC supply between red and black; return voltage 0.5–4.5 V proportional to system pressure

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  5. Electronic Expansion Valve (EEV) Coils

    • 5-Wire / 6-Wire Coils:

      • Resistance range: 45 – 50 Ω between control wires.

      • “J Series” high-resistance coils: ~150 Ω per winding

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      • Always test coil to earth (O/L expected).

  6. Thermistor Reference Table

    • Standard resistance at 20 °C:

      • Room Temp = 12.5 kΩ, HEX = 62.9 kΩ, Compressor = 62.5 kΩ.

      • Voltage typically 2.1–2.3 V DC at 20 °C

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  7. Test Run Procedure

    • Manual test run can be activated from the outdoor LED display board if wall controller access is unavailable.

    • Always terminate test run at the display after completion to return control to the wall controller

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Technician Notes

  • Always isolate power before performing resistance or diode tests.

  • Verify readings against ambient temperature (especially thermistors and motors).

  • Cross-check anomalies using the Mobile Technician App for updated specifications.

  • Faulty readings may indicate shorted diodes, open circuits, or PCB failure.