Fujitsu VRF Communication PCB (Board) Testing

Procedure: Testing Communication PCB (Outdoor to Indoor)

Step 1: DC Voltage Test at Terminals X1/X2 (System Powered)

Purpose: Verify communication voltage from the outdoor PCB to the indoor unit.

Instructions:

1. Ensure the system is powered on.

2. At the outdoor terminal block, measure DC voltage across terminals X1 and X2.

3. Expected Result:

   • A pulsed DC signal of approximately ±30–35 VDC (typically ~32 VDC).

Troubleshooting:

• If voltage is absent or below 10 VDC, suspect a faulty outdoor communication PCB.

Step 2: Communication Loop Resistance Check (System Powered Off)

Purpose: Verify the integrity of the communication loop wiring and indoor PCB.

Instructions:

1. Power off the system completely.

2. Disconnect the wires at X1/X2 on the outdoor terminal block.

3. Using a multimeter, measure resistance downstream (toward the indoor unit).

Expected Resistance:

• Normal range: 60–65 Ω

• Minimum acceptable: 58 Ω

Troubleshooting:

• If reading is OL (open loop) or <50 Ω:

  • Check for loose or corroded connections

  • Inspect for shorts to ground

  • Suspect a failed indoor PCB or RB unit