An E320 Error will occur when the OLP (Overload Protection Sensor) is detected as open or short circuit by the outdoor main PCB.
The OLP sensor is a thermistor that sits on top of the compressor.
The OLP sensor has a reading of around 200K Ohm at 25 degrease.
If the OLP sensor is reading correctly with a multi meter then a faulty outdoor main PCB would be the most likely cause of the OLP error.
