Purpose
This document provides a comprehensive set of test procedures and expected readings for diagnosing key electrical and electronic components in Fujitsu air conditioners.
It is intended for qualified service technicians to confirm component condition before replacement
1. Communication and Signal Tests
System Signal Test:
Measures communication between indoor and outdoor units.Test between Terminal 2 (Neutral) and Terminal 3 (Signal).
Expected indoor static voltage: 40–295 V DC depending on model type.
Expected outdoor voltage: 3–120 V DC
3-Wire Remote Signal Test:
Y1–Y3 = 12 V DC supply.
Y3–Y2 = 7–12 V DC fluctuating pulse.
If 12 V DC is missing, controller PCB may be faulty
2. PCB Layout and Voltage Checks
Page 12 diagram shows the main outdoor PCB layout and nominal voltages:
Fan motor: 330–370 V DC (red-black), 15 V DC (white-black)
EEV coil: 12 V DC
Thermistors: 5 V DC
High-pressure sensor: 5 V DC
Reversing valve: 240 V AC (energised in heating mode)
Fujitsu Component Testing (1)
3. Power Conversion and Inverter Modules
| Component | Test Mode | Expected Values | Remarks |
|---|---|---|---|
| ACTPM (Active Filter Module) | Resistance (kΩ) | + 360 kΩ; L1 360 kΩ; L2 >1 MΩ; N 0 Ω; + P 720–900 kΩ | Short circuit will trip breaker Fujitsu Component Testing (1) |
| IPM (Inverter Power Module) | Diode | PU/V/W = 0.4 V each; PN = 0.7–0.9 V | Disconnect harness before test |
| Diode Bridge (1-Phase) | Diode | ~ to + / – = 0.4 V; + to – = 0.7–0.9 V OL reverse | Converts AC → DC 200–230 V |
| Diode Bridge (3-Phase) | Power ON: 560–600 V DC (+ to –) | L1-L3 = 400–415 V AC; L-Earth = 230–240 V AC Fujitsu Component Testing (1) |
4. DC Fan Motor Test (Power OFF)
Operates on 330–380 V DC supply and 15 V DC control.
Diode Test Expected:
Red-Black = O/L
Red-White = 0.5–1.8 V (older ≈ 0.5 V / newer ≈ 1.8 V)
Black-Red = 0.8–1.1 V
Black-White = 0.4–0.6 V
Do not disconnect under power
5. Thermistor Testing
Power ON:
Supply = 5 V DC; Return < 5 V DC.
Compare measured return voltage against the thermistor chart (e.g., 20 °C ≈ 2.2 V, 12.5 kΩ).
Power OFF:
Measure resistance in kΩ; confirm readings match temperature chart.
Inspect for damage or earth shorts
6. Electronic Expansion Valve (EEV) Coil Tests
| Type | Test Mode | Expected Resistance | Notes |
|---|---|---|---|
| 5-Wire EEV | Resistance | 45–50 Ω each (RED to WHITE/ORANGE/YELLOW/BLUE) | O/L to Earth = Normal |
| 6-Wire EEV | Resistance | 45–50 Ω each pair (RED to WHITE/ORANGE, BROWN to YELLOW/BLUE) | Always test to Earth |
| High-Res J-Series 6-Wire | Resistance | 150 Ω each coil; 300 Ω across pairs | Indicates high impedance type |
7. Pressure Transducer
Power ON: Red-Black = 5 V DC, Black-White = return voltage (~ 2.8 V = 2875 kPa).
Power OFF (Diode Test):
Black-White = 1.0–1.1 V
Black-Red = 1.2–1.3 V
White-Red = 1.6–1.7 V
Reverse = 0.5–0.7 V
8. Thermistor Reference Table (20 °C)
| Location | Resistance (kΩ) | Voltage (V DC) |
|---|---|---|
| Room Sensor | 12.5 kΩ | 2.22 V |
| Indoor HEX | 62.9 kΩ | 2.21 V |
| Discharge Sensor | 64.5 kΩ | 0.84 V |
| Compressor Sensor | 62.5 kΩ | 0.86 V |
| Outdoor HEX | 6.1 kΩ | 2.19 V |
| Outdoor Ambient | 12.6 kΩ | 3.76 V |
9. Quick-Reference Summary Tables
Page 25–27 consolidate readings for:
ACTPM
IPM
DC Fan Motor
1-Phase and 3-Phase Diode Bridges
Pressure Transducer
DC Signal levels (Indoor/Outdoor)
Multi-head signal chip resistances (1.5–2 MΩ)
10. Test Run
If the wall controller is unavailable, a manual test run can be initiated using the Outdoor Unit LED Display Board.
Press the SW2 test switch—the LED indicators confirm operational modes.
Ensure to exit test mode manually to return control to the wall controller
Summary
These component test sheets form a reliable reference for fault diagnosis of Fujitsu inverter systems.
They enable technicians to confirm circuit integrity, verify DC/AC power conversion, and validate sensor operation without unnecessary part replacement.