Communication or Indoor Fan Motor Fault

What does 3-time blink 2.5-second OFF mean?

This code signifies one of two distinct issues depending on the operating context: either the serial communication signal from the outdoor unit is not received for up to 6 minutes, or the indoor fan motor's rotational frequency feedback signal is absent for 12 seconds after operation. Both conditions prevent the indoor unit from operating correctly, resulting in a lack of airflow or complete system shutdown. Timely resolution is crucial for proper unit function and comfort.

• Loss of serial communication (CNV, CMV, CNP signals) between the indoor and outdoor units due to cable breakage or loose connections (e.g., on terminal block TB7).
• Electromagnetic interference (EMI) disrupting the communication signal integrity, especially if power and signal cables are run in parallel without proper shielding.
• Indoor fan motor (ECM type) failure, preventing it from rotating or providing tachometer feedback, often due to internal winding short or bearing seizure.
• Indoor fan motor control circuit on the indoor P.C. board failing to provide proper drive signals or process feedback (FG signal) from the motor.
• Incorrect addressing or DIP switch settings (e.g., SW1) on indoor or outdoor units preventing proper communication handshake.

Click steps to track your progress.

1. 1

   Isolate power to both indoor and outdoor units at the main disconnect switch.

2. 2

   Inspect the serial communication wiring (CNV, CMV, CNP) between indoor and outdoor units, checking for physical damage, loose terminals (e.g., TB7), and proper insulation. Verify wire gauge and length meet specifications.

3. 3

   Use a multimeter to check for continuity on each communication line (CNV, CMV, CNP) and for any shorts between lines or to ground.

4. 4

   If communication lines are verified, access the indoor fan motor. Check for free rotation of the fan blade by hand (with power OFF). Measure motor winding resistance if applicable.

5. 5

   Verify the indoor fan motor feedback signal (FG) is present and within specified voltage range at the indoor P.C. board connector (e.g., J01) using an oscilloscope while the unit is attempting to run.

6. 6

   If communication fault persists, check DIP switch settings (e.g., SW1 on indoor unit, SW7 on outdoor unit) for correct addressing and operating mode as per installation manual.