Copyright Goodheart-Willcox Co., Inc. Chapter 17 Electrical Troubleshooting Fundamentals 385 6 diagram of a refrigerator may show the condensing unit at the bottom of the diagram and the freezer fan at the top of the diagram. This type of pictorial diagram helps to locate the component on a unit for troubleshooting. 17.3 Electrical Troubleshooting Process Electrical problems are the cause of many service calls. The problem could be as simple as a tripped circuit breaker or as complex as a fault tripped on a low-voltage circuit board. Due to the frequency of problems with the electrical system and the relative ease of initial electri- cal checks, electrical tests are often a good start when troubleshooting. Chapter 3, Service Calls, introduced a general system- atic troubleshooting procedure shown in Figure 17-17. An understanding of the electrical subsystem, its operation, and strategies for testing and identifying faults is critical to successful troubleshooting. Specifically, the technician must consider the following about the electrical subsys- tem while troubleshooting: • Electrical diagrams, electrical component specifications, and troubleshooting charts provided on the equipment access panel or in manufacturer’s service material. Goodheart-Willcox Publisher Figure 17-14. The switch on the top rung is open, preventing current from flowing through the light. The switch on the lower rung is closed, completing the connection between the two rails and allowing current to flow between them. The fan motor (load device) shown on the lower rung is energized. Switch open, no current in rung Thermostat closed, circuit completed Fan motor energized (on) Light bulb is de-energized (off) Goodheart-Willcox Publisher Figure 17-13. This illustration shows some common switching device symbols used in electrical diagrams. Symbols vary slightly from manufacturer to manufacturer. Switching Devices Single-Pole, Single-Throw Switches Contacts Open Closed Normally Open (NO) Normally Closed (NC) Common Switches Normally Open, Close on Rise Normally Open, Close on Fall Normally Closed, Open on Fall Normally Closed, Open on Rise Temperature Switch Pressure Switch Flow Switch