LineMini-Split Heat Pump Series
41codes
/
Fault

F3Compressor Out-of-Step Error

LED

What it means

The module panel monitors current on the compressor lead wires and calculates rotor position during operation. When the compressor deviates far from normal status — due to excessive current or inability to detect rotor position — this error is indicated. It frequently follows F1 (Module Protection Error) and shares a similar diagnostic approach.

Special attentionF3 (compressor out-of-step) and F1 (module protection) are both abnormal compressor operating conditions — F3 is calculated by the module panel's main chip, while F1 is detected by the power module itself. When diagnosis is uncertain for either, analyze both errors together using the same method. For inverter units in poor electrical environments or older units, occasional occurrences of these errors represent normal protection behavior.

Inspection path

1Supply voltage→2Compressor wire and reactor wire→3System pressure→4Module panel→5Main external control panel→6Compressor

Diagnostic procedure

  1. Check if the compressor wire order is correct. If reversed, try swapping the U-V phase wires.
  2. Verify supply voltage stability. Measure system pressure — high pressure causes compressor rotation problems.
  3. Confirm the module panel is firmly mounted to the radiator. Check if heat exchangers are dirty, causing elevated system pressure.
  4. If the error appears immediately on startup, inspect for strike-arc damage. Verify equal resistance between any two compressor wires (ohm-level, equal across all pairs). Verify insulation resistance of each compressor wire to earth (MΩ level). Also check whether DC voltage between P and N is too high (above 200V). Confirm the reactor wire is sound.
  5. Test that the 15V and 5V (or 3.3V) power supplies on the module panel are stable.
  6. Replace the module panel with a known-good unit. If the unit runs normally after replacement, the original module panel is damaged.
  7. After ruling out module, wiring, system, and power supply issues, listen to the compressor. If only electromagnetic sound is present without startup, or if the compressor runs irregularly before shutdown, the compressor may be blocked or damaged.

Tools

  • Multimeter
  • Pressure gauge
  • Module panel in normal working condition

Frequent parts

  • Supply voltage
  • Compressor wire
  • Reactor
  • Module panel
  • Main external control panel
  • Compressor

Related codes

F1Module Protection Error
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