ACiQ EH02 Error Code

What does ACiQ EH02 mean?

EH02 is a zero-crossing signal detection error. The indoor control relies on detecting the point where the AC power waveform crosses zero to time its operation; when that zero-crossing signal is not detected correctly, the indoor unit reports EH02 and the related TS03 procedure is used to diagnose it.

Symptoms

• EH02 shown on the indoor unit display
• Indoor unit does not run normally
• Fault tied to the incoming AC power signal detection

Common causes

• Abnormal or unstable incoming AC power signal
• Faulty indoor main PCB zero-crossing detection circuit
• Wiring or power-supply problem affecting the indoor board

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Diagnostic steps

1. Power cycle the unit

   Turn the unit off, wait, then restart and observe whether EH02 reappears.

2. Check the power supply

   Verify the indoor unit is receiving stable AC power within its rated range.

3. Inspect indoor wiring

   Confirm power and control wiring to the indoor board is properly connected and undamaged.

4. Have the indoor board evaluated

   If power is normal and the code persists, the indoor PCB's detection circuit should be checked per the TS03 procedure.

When to call a professional

EH02 involves the indoor board's power-signal detection circuit and live AC measurements. If a power cycle and a basic supply check do not clear it, contact a licensed HVAC technician. Working inside the indoor unit on the control board, where stored charge can remain after power-off, should be handled only by a qualified service professional following the manufacturer's diagnostic procedure.