In this article, we will address a common issue in inverter air conditioners where the unit powers on but shuts off approximately 10 seconds later without any apparent reason.
Inverter Compressor Operation
Inverter compressors start at low speeds to avoid power surges and optimize energy consumption. The system controls both frequency and voltage, gradually increasing speed according to cooling demand. This design protects components, reduces mechanical stress, and extends the unit’s lifespan.
However, for proper operation, the compressor must generate sufficient torque at low frequencies, which relies on precise synchronization with the control board.
Possible Causes and Solutions
1. Excessive Current Consumption
The compressor might be drawing more current than allowed due to a motor issue.
Diagnosis:
- Check if the unit displays an error code and consult the manual for its meaning.
- If no code appears, measure the current draw with a clamp meter and compare it to the maximum value indicated on the unit’s label.
- If the current exceeds the LRA (Locked Rotor Amperage) value, it could be an electrical problem.
2. Faulty Electrical Connections
Damaged cables or loose connections can cause failures.
Diagnosis:
- Disconnect the compressor and measure the resistance between its pins using a multimeter set to the ohms scale.
- Ensure the values are neither 0 nor infinite and that all three measurements are nearly identical.
3. Faulty Intelligent Power Module (IPM)
A defective IPM can cause the compressor to shut down prematurely.
Diagnosis:
- Fully disconnect the unit before proceeding.
- Set the multimeter to diode mode and identify the IPM model number.
- Measure phases U, V, and W using the following steps:
Step A: Place the red probe on the IPM’s negative (ground) pin and the black probe on pins U, V, and W in sequence.
Step B: Reverse the probes, placing the black one on the positive pin and measuring U, V, and W again. - Values should be consistent. Any significant disparity indicates a faulty module.
4. Short Circuit in the PFC Circuit
The power factor correction (PFC) circuit may be malfunctioning due to faulty capacitors.
Diagnosis:
Inspect the capacitors and replace them if necessary.
5. False Overload Alarm
If the current measured in step 1 is normal, it may be a false alarm triggered by the overload switch.
Diagnosis:
- Temporarily bypass the overload switch to see if the issue resolves.
6. Refrigerant Leak
A refrigerant leak can reduce current draw and cause the unit to shut off automatically due to insufficient cooling.
Diagnosis:
- Measure the current draw; if it’s lower than normal, check for refrigerant leaks.
- Look for an error code related to the leak before the unit powers off.
