LineMini-Split Heat Pump Series
41codes
/
Fault

F5Compressor Top Head Sensor Error

LED

What it means

The compressor top head sensor is typically a temperature protection switch that remains closed (short circuit) under normal temperature and opens (open circuit) when temperature is too high. The main external control panel indicates this error when it detects disconnection of this switch.

Special attentionThe compressor top head sensor is a simple, reliable temperature switch and rarely fails on its own. Direct diagnostic attention to system pressure and actual compressor temperature before assuming sensor failure. Note: LED pattern ○ ● ○ (LED1 off, LED2 on, LED3 off) also indicates compressor shell temperature protection and is diagnosed using the same procedure as F5.

Inspection path

1Compressor top head temperature (check if genuinely above 110°C)→2Compressor top head sensor (temperature protection switch)→3Sensor wire→4Connectors→5Main external control panel

Diagnostic procedure

  1. First check if the compressor top head temperature is genuinely too high (above 110°C), which would trigger the protection switch. Common causes: refrigerant shortage causing the compressor to idle, or system blockage creating excessive pressure.
  2. After ruling out system issues, test the sensor terminals with a multimeter. The temperature protection switch is normally closed — an open circuit indicates a sensor or lead wire problem.
  3. Inspect the sensor wire and connecting wire for damage.
  4. Verify all terminal connectors are firmly seated.
  5. Disconnect power and use a metal conductor to short-circuit the compressor top head terminal on the main external control panel. If the error disappears after restarting, replace the sensor. If the error persists, replace the main external control panel.

Tools

  • Pressure gauge
  • Multimeter

Frequent parts

  • System pressure
  • Refrigerant level (liquid shortage)
  • Compressor top head sensor (temperature protection switch)
  • Main external control panel
SafetyDisconnect 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 Reference6

Recirculated

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

External temperature

15 kΩ @ 25°C
Too-high resistanceDetected outdoor temperature reads lower than actual, causing incorrect temperature-based control decisions.
Too-low resistanceDetected outdoor temperature reads higher than actual, causing incorrect temperature-based control decisions.
TriggersF6External Temperature Sensor Error

Exhaust

50 kΩ @ 25°C
Too-high resistanceDetected exhaust temperature reads lower than actual. The system may fail to activate protection when exhaust temperature is genuinely dangerous.
Too-low resistanceDetected 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.
TriggersP5Exhaust ProtectionF4Exhaust Sensor Error

Internal coil

20 kΩ @ 25°C
Too-high resistanceDetected temperature reads lower than actual. May cause high-pressure cold-blast protection during heating or frequent anti-freezing protection during cooling.
Too-low resistanceDetected temperature reads higher than actual. May cause frequent overheat protection during heating or overload protection during cooling.
TriggersP7Anti-Freezing Protection in Refrigeration ModeP6Indoor High Temperature ProtectionE3Internal Coil Sensor Error

External coil

20 kΩ @ 25°C
Too-high resistanceDetected temperature reads lower than actual. May cause frequent entry into defrost mode, illusory defrost cycles, or protection errors during cooling.
Too-low resistanceDetected temperature reads higher than actual. May cause defrost failures during heating or protection activation during cooling.
TriggersP4Refrigeration Overload ProtectionE2External Coil Sensor Error

Internal temperature

15 kΩ @ 25°C
Too-high resistanceDetected temperature reads lower than actual. May cause shutdown errors in heating mode or startup failures in cooling mode.
Too-low resistanceDetected temperature reads higher than actual. May cause startup errors in heating mode or shutdown failures in cooling mode.
TriggersE1Internal Temperature Sensor Error