First of all, I think there is nothing wrong with the motherboard. Secondly, you said that the zero fire line of internal unit 220 was opened? Is that because you didn't put the internal transformer aside and turn on the relay of the plate fan pressure when you measured it? What do you mean? Maybe your measurement method is incorrect. If your air conditioner has overcurrent detection, it is mostly overcurrent detection. If there is no overcurrent detection circuit, there may be something wrong with the starting capacitor of the compressor. If all the above are normal, it may be that the pipeline is a little blocked (pipeline screen). Please check them one by one. Chengdu-Yang Qingshu! !