Copyright Goodheart-Willcox Co., Inc. Chapter 17 Electrical Troubleshooting Fundamentals 387 6 • Sequence of operation for electrical devices and the controlled components. • Consideration of low-voltage control circuits and high-voltage power circuits. • Expected voltage, current, and resistance measurements within the circuits based on system conditions. The electrical subsystem is considered during each step of the troubleshooting procedure: • Customer interview. Ask the customer about recent work performed at the home or business, such as work that involved the electrical system. Ask the customer about any unusual sounds or smells they may have experienced while the system was operating. • Initial inspection. Carefully inspect electrical components and devices throughout the system. Look for loose connections, corroded contacts, bulging capacitors, damaged components, and other potential issues. Look for signs of prior melting or sparking at terminals and connections. • Identify system malfunction, test to find cause. Electrical testing and troubleshooting occurs during this troubleshooting step. Voltage and current measurements are used to verify proper systems operation. These measurements may indicate a potential fault in an electrical device, which can then be tested. Often, system testing begins with the electrical subsystem. • Repair. The electrical system is always considered during the repair step. Even if the repair does not directly involve the electrical system, you must consider the location of electrical conductors and components to ensure that you are working safely. • Test system for proper operation. Final testing typically includes some electrical testing, such as measuring the current draw of a compressor. Electrical testing generally follows basic steps as shown in Figure 17-18. First, check the thermostat to ensure it is set correctly (for example, calling for heat or cool as appropriate with an appropriate set point). This check is generally performed as part of the initial inspec- tion of the system. Second, measure voltage at various points to ensure readings are as expected. This voltage check may include both the low-voltage control circuit and Understanding Correct System Operation • Expected measurements • Sequence of operation Subsystem Considerations • Airflow • Electrical • Mechanical/refrigerant • Combustion Resources • Equipment troubleshooting codes • Equipment troubleshooting charts • Equipment wiring diagrams • Equipment service information General Systematic Troubleshooting Procedure Customer Interview Initial Inspection Identify System Malfunction, Test to Find Cause Repair Test System for Proper Operation Troubleshooting Steps Informed By: Goodheart-Willcox Publisher Figure 17-17. Understanding the correct operation of the electrical system and making use of manufacturer provided diagrams, charts, and manuals are critical requirements for executing a troubleshooting process. Device and Component Testing to Identify or Confirm Fault Electrical Testing Procedure Check Thermostat Display and Settings Voltage Testing (Line and Control) to Identify Fault Investigate Root Cause of Fault Goodheart-Willcox Publisher Figure 17-18. This basic electrical testing procedure can be used during the testing phase of the troubleshooting process. There are many electrical testing methods. Be sure whatever method you use is systematic and thorough.