Indoor unit displays P4 and system may not start or may shut down quickly.

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Faulty inverter power module on outdoor PCB, Shorted compressor, Poor heat sinking of inverter module, Power surge damage

How to Fix / Troubleshooting

Safety first: This is a complex high-voltage inverter fault. Turn off power and do not attempt internal board repairs unless you are a trained technician.

User actions:

Power reset: Turn off the outdoor disconnect for 10 minutes, then restore power and test.
Check ventilation: Ensure the outdoor unit is not blocked and that the control compartment is not excessively hot.

Professional repair: Persistent P4 usually requires replacement of the outdoor inverter control board and possibly the compressor. Contact a licensed HVAC technician.

Repair Difficulty

Professional Required 5/5

Required Part

Outdoor Inverter Control Board

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