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Mitsubishi Electric Aircon 04 / LED1 Lit, LED2 4x

Capture the Mitsubishi Electric 04 / LED1 lit, LED2 4x fault correctly, then see what should be checked before parts are quoted.

What does Mitsubishi Electric 04 / LED1 lit, LED2 4x mean?

Mitsubishi Electric 04 / LED1 lit, LED2 4x is listed as fin temperature or P.C. board temperature thermistor in Multi-Split rows such as FP Series, Starmex R32. This meaning comes from the manufacturer's own diagnostic material. Confirm the exact model, series, or signal row before accepting a parts quote.

  • Open, shorted, displaced, or out-of-range thermistor or pressure-sensor reading.

  • Loose sensor connector, damaged sensor harness, or water-affected wiring.

  • PCB input fault after the sensor and wiring readings are confirmed.

What to do now

Use these steps before customer action, a sensor check, or PCB quote.

  • Treat it as a fault signal

    If 04 / LED1 lit, LED2 4x remains displayed or cooling is still abnormal, preserve the code and arrange diagnosis.

  • No manufacturer reset steps listed for 04 / LED1 lit, LED2 4x

    Capture the complete 04 / LED1 lit, LED2 4x pattern and model stickers first. The manufacturer lists no customer reset procedure; do not treat a generic power-cycle as manufacturer guidance.

  • Send these to us

    04 / LED1 lit, LED2 4x blinking light, a short video of the blinking-light sequence, Mitsubishi Electric model stickers, affected rooms, operating state when the code appeared, and when the fault appears

Guidance for your model

Notes that match the code to your exact model. Electrical, refrigerant, wiring, resistance and component checks are for a technician.

  • Detail
    Diagnostic note
    What it says
    Do not keep resetting the system if this pattern returns. Record the model number, lamp or LED pattern, and affected rooms before booking diagnosis.
  • Detail
    Singapore / model note
    What it says
    Official Mitsubishi Electric checklist action: Check outdoor thermistors or replace inverter P.C. board.
  • Detail
    Singapore / model note
    What it says
    Official Mitsubishi Electric checklist action: Check outdoor thermistors or replace control P.C. board.

What to check before repair

Use this split to separate safe evidence capture from the tests a technician should prove before quoting parts.

  • You can check
    Before taking any system action on 04 / LED1 lit, LED2 4x, take a short video of the blinking-light sequence.
    Technician should confirm
    Confirm which sensor 04 / LED1 lit, LED2 4x maps to on the exact model table.
  • You can check
    Capture the Mitsubishi Electric indoor and outdoor model stickers so the correct family row is used.
    Technician should confirm
    Measure the sensor value against the service-manual resistance or voltage range.
  • You can check
    The manufacturer lists no customer reset procedure for this code. Note whether one room, several rooms, or the whole system is affected.
    Technician should confirm
    Check connector condition, harness continuity, and PCB input before replacing boards.

What changes the next step

These clues decide whether the first check is room-side, shared outdoor-side, refrigerant-side, listed-meaning, or model-family confirmation.

  • What you see
    Only one indoor unit shows 04 / LED1 lit, LED2 4x.
    What it points to
    The affected room, indoor board path, wiring route, or local component should be checked first.
  • What you see
    Several rooms or the outdoor unit show the same 04 / LED1 lit, LED2 4x fault.
    What it points to
    Prioritise the reporting-unit sensor circuit, shared harness path, and control-board input.
  • What you see
    The fault appears immediately even before the unit cools properly.
    What it points to
    Sensor value, connector, harness, and PCB input should be tested in that order.
  • What you see
    The model family is different from the row you found online.
    What it points to
    Use the model or series filter first; same-looking codes can still belong to different diagnostic tables.
  • What you see
    The model belongs to Multi-Split rows such as FP Series, Starmex R32.
    What it points to
    This meaning comes from the manufacturer's own diagnostic material. Match the code to your model's listing before parts are quoted.

Sensor or PCB decision

Mitsubishi Electric 04 / LED1 lit, LED2 4x is usually repair-first if a sensor or harness reading is confirmed. Board replacement should wait until the sensor circuit is tested.

  • Sensor replacement is usually targeted when resistance or voltage readings are out of range.

  • Harness or connector damage can look like a sensor fault until continuity is checked.

  • PCB replacement is a later step if the sensor and wiring test correctly.

Mitsubishi Electric 04 / LED1 lit, LED2 4x questions

What does the Mitsubishi Electric 04 / LED1 lit, LED2 4x error mean?
Mitsubishi Electric 04 / LED1 lit, LED2 4x is listed as fin temperature or P.C. board temperature thermistor in Multi-Split rows such as FP Series, Starmex R32. This meaning comes from the manufacturer's own diagnostic material. Confirm the exact model, series, or signal row before accepting a parts quote.
Can I fix a Mitsubishi Electric 04 / LED1 lit, LED2 4x error myself?
No. 04 / LED1 lit, LED2 4x needs a technician's measurement before parts are decided. Before taking any system action on 04 / LED1 lit, LED2 4x, take a short video of the blinking-light sequence. Capture the Mitsubishi Electric indoor and outdoor model stickers so the correct family row is used.
Is it safe to keep running the aircon with a 04 / LED1 lit, LED2 4x error?
If 04 / LED1 lit, LED2 4x remains displayed or cooling is still abnormal, preserve the code and arrange diagnosis.
What causes a Mitsubishi Electric 04 / LED1 lit, LED2 4x error?
Open, shorted, displaced, or out-of-range thermistor or pressure-sensor reading. Loose sensor connector, damaged sensor harness, or water-affected wiring. PCB input fault after the sensor and wiring readings are confirmed.
Will a Mitsubishi Electric 04 / LED1 lit, LED2 4x error need a repair or a full replacement?
Mitsubishi Electric 04 / LED1 lit, LED2 4x is usually repair-first if a sensor or harness reading is confirmed. Board replacement should wait until the sensor circuit is tested.
What should I send a technician about a Mitsubishi Electric 04 / LED1 lit, LED2 4x error?
Before booking, send: 04 / LED1 lit, LED2 4x blinking light, a short video of the blinking-light sequence, Mitsubishi Electric model stickers, affected rooms, operating state when the code appeared, and when the fault appears.

Where to go next

Confirm the fault

Share the error code, model number and symptoms so we can assess the likely cause.