The H5 error code in an air conditioner indicates that the Intelligent Power Module (IPM) has entered protection mode. This is typically due to issues with electrical supply or elevated temperature. The IPM, located on the outdoor unit’s electronic board, manages and supplies power to the inverter compressor.
Below is a systematic guide to identifying the causes and resolving this error:
Common Causes of H5 Error Code
- Electrical supply issues
- Low voltage in the power supply.
- Faulty electrical connections or loose contacts.
- Overcurrent caused by system failures.
- Mechanical or cooling problems
- Malfunctioning outdoor unit fan.
- Dirty heat exchanger causing system overpressure.
- Compressor faults
- Abnormal electrical resistance between compressor pins or current leakage to the ground.
- Overheating of the IPM module
- Misaligned heat sink fins or lack of thermal paste.
- Internal faults in the IPM’s IGBT transistors.
- Faulty PFC Circuit
- Incorrect DC voltage at the rectifier bridge output.
- Damaged components such as coils, resistors, diodes, or capacitors.
Steps to Resolve the H5 Error
1. Initial Check
- Disconnect the unit from the power supply for at least 5 minutes.
- Reconnect the unit and check if the error disappears.
2. Basic Electrical Inspection
- Use a multimeter to measure the voltage supply from the electrical network.
- If overcurrent is detected, inspect all electrical connections and cables for loose contacts.
3. Check the Fan and Heat Exchanger
- Ensure the fan is operating correctly.
- Clean the heat exchanger to remove dirt buildup.
4. Inspect the Compressor
- Disconnect the compressor and measure the resistance between the pins using a multimeter:
- All resistance values should be equal and never show infinity.
- Resistance between the pins and the casing should be infinite to rule out current leakage to the ground.
5. Diagnose the IPM Module
Preparation
- Ensure the capacitors are discharged before handling the board.
- Locate the IPM module, usually covered by heat sink fins.
Electrical Testing of the IPM Module
- Set the multimeter to diode mode.
- Test the internal diodes of the transistors:
- Place the black probe on the positive input and the red probe on the U, V, and W outputs.
- The readings should be approximately 0.45 V.
- Repeat the process, reversing the probes to test the negative connection.
6. Inspect the PFC Circuit
- Check the DC voltage after the rectifier bridge:
- For 110V AC, the voltage should be approximately 150V DC.
- For 220V AC, it should be around 300V DC.
- If the voltage is correct, verify the electrical continuity of the coil and resistors in the PFC circuit.
- Visually inspect the capacitors and use a capacitance meter to check their condition.
7. Check Heat Dissipation
- Ensure the heat sink fins are properly aligned.
- Verify the presence of thermal paste to ensure proper heat transfer.
