General Assist Technical Reference
Error 63.1 - Inverter Current Trip
Diagnosis of inverter overcurrent faults during compressor start-up or operation
Error 63.1 indicates that the inverter protection circuit has detected excessive compressor current. The fault may be caused by the compressor, inverter PCB, supply conditions or a problem within the compressor power circuit.
Electrical safety: Inverter circuits contain high DC voltage and may remain charged after power is isolated. Testing must only be completed by qualified service personnel using suitable instruments and safe working procedures.
1. Fault overview
Error 63.1 is an inverter current trip fault. It normally occurs when the inverter detects current above its protection threshold while starting or driving the compressor.
| When the fault occurs | Possible cause |
|---|---|
| Immediately as the compressor attempts to start | Locked or electrically damaged compressor, shorted output circuit, inverter PCB or IGBT fault |
| After the compressor has operated for a short period | Compressor load issue, unstable supply, inverter overheating, intermittent wiring or inverter PCB fault |
2. Inverter PCB LED diagnostic reference
Observe the LEDs on the inverter PCB before resetting the system. The retained LED pattern can indicate whether the current trip occurred during the latest start attempt or during previous operation.
| Condition | LED1 | LED2 | LED3 | LED4 | Indication |
|---|---|---|---|---|---|
| This time | 6 blinks | ON | ON | OFF | Current trip occurred at compressor start-up |
| Previously | 6 blinks | OFF | ON | OFF | Current trip occurred during operation |
Important: Record the LED pattern before cycling power. Resetting the system may remove useful diagnostic history.
3. Diagnostic procedure
1
Observe the fault timing.
Determine whether Error 63.1 occurs immediately at compressor start-up or only after the compressor has operated.
Determine whether Error 63.1 occurs immediately at compressor start-up or only after the compressor has operated.
2
Record the inverter PCB LEDs.
Compare the LED pattern with the reference table above before resetting power.
Compare the LED pattern with the reference table above before resetting power.
3
Check the electrical supply.
Confirm the supply voltage is stable. For three-phase units, check phase-to-phase voltage and verify that the phases are reasonably balanced.
Confirm the supply voltage is stable. For three-phase units, check phase-to-phase voltage and verify that the phases are reasonably balanced.
4
Inspect compressor wiring.
Check the inverter output terminals, compressor plugs and harnesses for loose terminals, corrosion, overheating, damaged insulation or signs of arcing.
Check the inverter output terminals, compressor plugs and harnesses for loose terminals, corrosion, overheating, damaged insulation or signs of arcing.
5
Measure compressor current.
Use a true RMS clamp meter and observe the current during start-up and ramp-up. Compare the reading with the compressor or unit nameplate data and the applicable service manual.
Use a true RMS clamp meter and observe the current during start-up and ramp-up. Compare the reading with the compressor or unit nameplate data and the applicable service manual.
6
Confirm inverter cooling.
Check outdoor fan operation, PCB heat-sink condition and airflow around the inverter compartment.
Check outdoor fan operation, PCB heat-sink condition and airflow around the inverter compartment.
Compressor current interpretation
| Observed behaviour | Likely direction |
|---|---|
| Current rises sharply and the system trips immediately | Investigate compressor electrical or mechanical failure, output wiring short or inverter output-stage fault |
| Current appears reasonable but the inverter repeatedly records a current trip | Investigate inverter PCB current sensing or IGBT circuitry |
| Current is unstable and supply voltage varies or phases are unbalanced | Correct the incoming supply before replacing components |
Do not diagnose from current alone. A rapid current rise may be caused by the compressor, the inverter output stage or a short within the power circuit. Complete the relevant compressor winding, insulation and inverter tests specified in the model service manual.
4. Corrective action summary
| Fault source | Evidence | Action |
|---|---|---|
| Compressor | Abnormal winding or insulation test, locked condition, or excessive current confirmed | Replace the compressor and inspect the refrigerant circuit and inverter output before recommissioning |
| Inverter PCB | Compressor and wiring test correctly but the current-trip fault repeats | Replace the inverter PCB using the correct part number, revision and configuration |
| Supply power | Low, unstable or unbalanced voltage | Correct the electrical supply and retest the system |
| Wiring or terminals | Loose, overheated, oxidised or damaged compressor connections | Repair or replace the affected harness, terminals or connectors |
5. Information to record before escalation
- Complete indoor and outdoor model numbers and serial numbers
- Whether the fault occurs at start-up or during operation
- Inverter PCB LED1 to LED4 pattern
- Supply voltage and, for three-phase units, phase balance
- Compressor current during start-up and immediately before the trip
- Compressor winding resistance and insulation-test results
- Condition of the inverter PCB, heat sink, fan operation and compressor wiring
Recommended diagnostic principle: Confirm the compressor, power supply and wiring condition before replacing the inverter PCB. This reduces repeat failures and unnecessary parts replacement.