Line Mini-Split Heat Pump Series
41 codes
/
Protection

P3 Liquid Deficiency Protection

What it means

System refrigerant level has fallen below 30%, resulting in a loss of cooling capacity and liquid shortage protection.

Inspection path

1 Outdoor unit stop valves (confirm fully open) → 2 Evaporator, condenser, and connection pipes (check for damage or leaks) → 3 Environmental and coil temperature sensors (check both simultaneously)

Diagnostic procedure

  1. Check the outdoor unit stop valves. Use a hex wrench to turn counterclockwise and confirm valves are fully open.
  2. Inspect the evaporator, condenser, and connection pipes for damage or cracks. Pay particular attention to weld points and pipe joints for refrigerant leakage.
  3. Use a multimeter to measure both the environmental temperature sensor and the coil temperature sensor at ambient temperature simultaneously. Abnormal resistance on both at the same time may suggest dual sensor failure rather than actual refrigerant loss.

Tools

  • Hex wrench
  • Multimeter
  • Pressure gauge

Frequent parts

  • Stop valve
  • Evaporator
  • Condenser
  • Connection pipe
Safety Disconnect power at the breaker before opening any access panel. DC bus capacitors retain charge for up to 5 minutes after disconnect — verify with a meter before touching live components.
Sensor Reference 6

Recirculated

20 kΩ @ 25°C
Too-high resistance Incorrect back temperature value affects electronic expansion valve adjustment and four-way valve position confirmation during heating.
Too-low resistance Incorrect back temperature value affects electronic expansion valve adjustment and four-way valve position confirmation during heating.
Triggers FA Recirculated Sensor Error

External temperature

15 kΩ @ 25°C
Too-high resistance Detected outdoor temperature reads lower than actual, causing incorrect temperature-based control decisions.
Too-low resistance Detected outdoor temperature reads higher than actual, causing incorrect temperature-based control decisions.
Triggers F6 External Temperature Sensor Error

Exhaust

50 kΩ @ 25°C
Too-high resistance Detected exhaust temperature reads lower than actual. The system may fail to activate protection when exhaust temperature is genuinely dangerous.
Too-low resistance Detected exhaust temperature reads higher than actual. The unit enters high exhaust temperature protection frequently, compressor frequency threshold rises, leading to unwanted shutdowns. Example: installing a 20KΩ coil sensor in place of the 50KΩ exhaust sensor produces this behavior.
Triggers P5 Exhaust Protection F4 Exhaust Sensor Error

Internal coil

20 kΩ @ 25°C
Too-high resistance Detected temperature reads lower than actual. May cause high-pressure cold-blast protection during heating or frequent anti-freezing protection during cooling.
Too-low resistance Detected temperature reads higher than actual. May cause frequent overheat protection during heating or overload protection during cooling.
Triggers P7 Anti-Freezing Protection in Refrigeration Mode P6 Indoor High Temperature Protection E3 Internal Coil Sensor Error

External coil

20 kΩ @ 25°C
Too-high resistance Detected temperature reads lower than actual. May cause frequent entry into defrost mode, illusory defrost cycles, or protection errors during cooling.
Too-low resistance Detected temperature reads higher than actual. May cause defrost failures during heating or protection activation during cooling.
Triggers P4 Refrigeration Overload Protection E2 External Coil Sensor Error

Internal temperature

15 kΩ @ 25°C
Too-high resistance Detected temperature reads lower than actual. May cause shutdown errors in heating mode or startup failures in cooling mode.
Too-low resistance Detected temperature reads higher than actual. May cause startup errors in heating mode or shutdown failures in cooling mode.
Triggers E1 Internal Temperature Sensor Error