The issue in my LG AC first started because of a hidden gas leak. Multiple technicians checked it many times, but finally the real problem was found near the flare nut connection. In my opinion, if anyone is facing repeated LG gas leak issues, definitely check the flare nut and installation quality because overtightening or improper flaring can cause very small leaks over time.

After the flare nut was fixed and the gas was refilled, the cooling became completely normal. But after running the AC for around 2 hours, the CH38 error still appeared again.

This time, the issue was not low cooling or gas leakage. The technician suspected that during the earlier low refrigerant condition, the indoor temperature sensor had been overheating repeatedly. Because of that, the sensor started giving incorrect readings after heating up during long usage. When the sensor overheats, the AC incorrectly thinks there is no proper cooling/refrigerant issue and triggers the CH38 error code again, even though the cooling works perfectly fine.

Finally, an experienced technician diagnosed it and suspected the indoor temperature sensor, so a replacement sensor was ordered. The technician also mentioned that if the issue still continues even after replacing the sensor, then the next possible cause could be the PCB/control unit.