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U1, UL

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

MHI · Air Conditioning

¿Qué significa U1, UL ?

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.

Causas comunes

  • 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.

Pasos de reparación & Lista de verificación

Haga clic en los pasos para seguir su progreso.

  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.

Ver todos los códigos en este manual (124)
Datos técnicos verificados. Última actualización: April 2026

Fallas relacionadas

00Outdoor Board LED only green lights up after startup - No outdoor unit of address 0 / Remote controller transmission wire open1OPERATION INDICATOR lamp blinks 1 time (Pattern A) - Indoor/outdoor unit communication error (Transmitting error - Outdoor unit)14OPERATION INDICATOR lamp blinks 14 times (Pattern A) - Other errors
Fuente: MHI Air Conditioning
Open Manual (Page 60)Buscar más códigos en este manual