In the automobile service job, the trouble of automatic air-conditioning system(auto-A/C) are increasing. The requirement of trouble shooting skill and high level knowledge of auto-A/C is increasing for the service engineers. To respond this recent trend, auto-A/C diagnosis simulator was manufactured and introduced for the service training lecture to raise the understanding of auto-A/C for the students. The results of questionnaire survey for the students show the effectiveness of the lecture using this diagnosis simulator.