A service technician is called to a small market, where the customer is complaining of products spoiling in a dairy case. After introducing himself and his company and handing the store owner a business card, the service technician carefully listens to the owner's account of the problem. The technician then politely asks the customer some pertinent questions in clear, concise, everyday language. Even though the questions are somewhat technical, the technician tries to not make the customer feel inept about any technical topics. Once the store owner shows where the dairy cases are located, the technician starts working. The technician takes the box temperature of the dairy case with a thermometer and finds it to be 47°F. The case is supposed to be holding product at 35°F to 39°F. While measuring the temperature of the dairy case, the technician notices that there is no airflow on one side of the case. A quick inspection of the evaporator section and evaporator fans indicates that one of the three PSC evaporator fan motors is not operating. The three fans are wired in parallel and operate off 230 V (see circuit diagram below). The run winding of the inoperative PSC fan motor has burned open. The technician suspects that the inoperative fan motor probably has an open winding. The service technician then opens the power disconnect switch and places a multimeter across the run winding of the inoperative fan motor. The meter reads 2 ohms.
