PURPOSE: To perform not only the initial diagnosis of trouble but also the accurate transmission of trouble data information to the operator in charge of repairing and to reduce a downtime by displaying the inspection item data and data of the person in charge of repairing, which are based on the preferential order stored in a memory means, on the basis of a display order for starting the diagnosis of trouble when trouble is generated in an apparatus.

CONSTITUTION: When trouble is generated in a heat exchanger system 4, the operator of this apparatus sends an order for starting the diagnosis of trouble to a CPU 11 from an input means 12. The CPU 11 accesses a memory means 7 to send the inspection item data for the diagnosis of the trouble of the heat exchanger system 4 and the data of the person in charge of repairing to a display means 8. By this method, a message is displayed on the display means 8. The operator of this apparatus checks the places concerned of the apparatus successively according to respective stages and, for example, when the abnormality of a pressure switch is discriminated, the abnormality of said stage is informed to a service man called up by phone. By this information, the service man confirms that the trouble is caused by the abnormality of a pressure switch to bring a new pressure switch and can recover the place to be repaired to a normal state immediately and the downtime of this apparatus is markedly reduced.