Upon arrival customer stated that system was not cooling as of last night it stopped working and that outdoor unit would never come on but the indoor unit would. After inspection of system found that defrost control board was showing an error code of “defrost operation” reset board and board then started to give an error code of “AMB sensor failure”. Tried to bypass sensor and reset system to see if system would come on and it stayed in the same lockout code. Will order new defrost control board and ambient temperature sensor when the supply house open back Monday morning 7/7/25. Advised customer of issue and let him know that I will check part availability when supply house is open, part and labor are covered under warranty due to customer maintaining regular routine maintenance of the equipment. Will check system operations when parts are replaced. System currently. Not working at this time.