Outdoor Board LED1 (green) blinks three times and LED2 (red) blinks four times alternately - Abnormal high pressure (High pressure switch 63H worked)

What does U1, UL mean?

During startup or operation, the outdoor unit's LED1 (green) blinks three times and LED2 (red) blinks four times alternately, indicating abnormal high pressure due to the high-pressure switch (63H) activating.

• Abnormal high pressure; high pressure switch (63H) activated.
• Indoor/outdoor units have a short cycle on their air ducts.
• Heat exchanger and filter are dirty or clogged.

Click steps to track your progress.

1. 1

   Check if indoor/outdoor units have a short cycle on their air ducts that could lead to high pressure.

2. 2

   Check if the connector (63H) on the outdoor controller board is not disconnected.

3. 3

   Check if the heat exchanger and filter are clean and not dirty.

4. 4

   Ensure the linear expansion valve is functioning correctly by measuring resistance values.