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1501 <1601> (U2)

1501 <1601> (U2) Refrigerant shortage trouble

Mitsubishi Electric · City Multi Air Conditioning Systems

What does 1501 <1601> (U2) mean?

This error indicates a low refrigerant level in the system. This can be caused by stop valves not fully open, defective sensors, or actual gas leakage.

Common Causes

  • Defective operation of stop valve (not fully open).
  • Defective thermistor.
  • Defective outdoor controller board.
  • Indoor LEV (Linear Expansion Valve) performance failure.
  • Gas leakage or shortage of refrigerant.
  • Defective 63HS sensor.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    Ensure all stop valves on the outdoor unit are fully open.

  2. 2

    Turn off the power to the unit at the circuit breaker for at least 5 minutes, then restart it.

  3. 3

    Visually inspect the refrigerant lines and outdoor unit for any signs of leaks, such as oily residue.

  4. 4

    If the error persists, contact a qualified HVAC technician.

  5. 5

    A technician will check for refrigerant leaks, measure refrigerant levels, and inspect sensors and valves.

Browse all codes in this manual (51)
Verified technical data. Last updated: April 2026

Related Faults

0403 (Ed)0403 (Ed) Serial communication error1102 <1202> (U2)1102 <1202> (U2) Compressor temperature trouble1302 <1402> (UE)1302 <1402> (UE) High pressure trouble
Source: Mitsubishi Electric City Multi Air Conditioning Systems
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