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ICP · Heat pump

4 Locked rotor

High severity ICP N4H3 Heat Pump

What the control is telling you

Compressor is not turning (locked rotor).

Applies to: ICP N4H3 R-410A split heat pump (manual 428 01 5103 02); Comfort Alert codes apply only to units factory-fitted with the Comfort Alert module

Likely causes

  • Failed run capacitor
  • Low line voltage
  • Excess liquid refrigerant in compressor
  • Seized compressor bearings

Test and repair steps

  1. Warning: Discharge capacitors before testing.
  2. Test the run capacitor; replace if failed.
  3. Measure line voltage at the unit under load; contact the utility if low at the disconnect.
  4. Check crankcase heater operation and for refrigerant flood-back.
  5. If capacitor and voltage are good, the compressor is likely seized - replace.

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Source: ICP N4H3 Installation Instructions 428 01 5103 02, Comfort Alert Diagnostics Codes (Figure 18), p.20. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.