TROUBLESHOOTING INSPECTION To locate faulty conditions in circuits, you need to perform some inspecting, some calculating, and some

instrument testing. A few moments spent studying the schematic or drawing of a particular circuit before the actual troubleshooting begins often simplifies the task of isolating the trouble. THINK! If a circuit fails to operate properly, apply some logical reasoning when you check for the fault. The trial-and-error method is inefficient and time-consuming.

A bad appliance should first be checked visually. If you fail to find the trouble by visual inspection, you will find that a meter is an indispensable device in testing electrical circuits of appliances.

Power Supply and Cord When you troubleshoot a circuit, the first thing you want to do is study the schematic; the next step is to inspect the circuit visually. Check for loose connections, loose wires, burnt wires, and burnt components, and check the type of wiring.

When you attempt to repair an inoperative appliance, do not be in a hurry to disassemble it to find the trouble. You should first pull the power cord from the outlet and determine if there is current at the outlet. If the outlet is energized, inspect the power cord. Next, examine the plug connections for cleanliness and tightness. Finally, inspect the power cord for any broken wires. If the condition of the cord makes it unserviceable, replace it before going any further in your troubleshooting procedure.

Careful inspection of electrical components and Checking the power supply and the condition of the equipment is essential to preventing fire hazards caused power cord should be the first thing you do when you by defects or dangerous conditions. These inspections attempt to find an electrical fault in an appliance. In a include checking for cleanliness, normal operation, number of cases, electrical faults are found in the power operation under load, tight connections, adjustment, cord, rather than in the appliance itself. Only when you and lubrication Always perform a visual inspection have determined that the fault is not with the power first. In this inspection, examine the general condition supply or cord, should you consider troubleshooting the of the equipment, determine whether it was abused, internal units. To troubleshoot these units effectively, dropped, or overloaded or is inoperative because of you have to disassemble part of the appliance.

continued use. The general condition of a unit can help you to determine the fault within it. Testing and maintaining equipment is best accomplished at the time of inspection. Completing everything without returning to the area saves time.

Tools and test equipment should be taken to the job site when the inspection is performed.

PREVENTIVE MAINTENANCE

WARNING When you are troubleshooting and doing repair work, TREAT ELECTRICITY WITH RESPECT. Working with electricity is hazardous, and you must take every precaution to avoid electrical shocks, burns, and electrocution. Regard all circuits as live until you have opened the switches or have made voltage tests and know that the circuit is dead. Lock and tag all switches in the OPEN position to keep other personnel from tampering with them and creating a safety hazardous condition. Remove protective devices, such as fuses, from their holders. REMEMBER, YOU WILL BE WORKING ON THAT CIRCUIT.

Controls and Elements Controls and elements on appliances or equipment will most likely be your biggest problem. Check

switches and controls with an ohmmeter for the making or breaking of contacts. If the switch is ON, the ohmmeter should read "0." The operation of a switch can be checked with a voltmeter. Check for voltage input and output.

7-14 New switches are usually inexpensive, so repairing an old one is not economical. The contacts may be reformed as a temporary measure to ensure a positive contact for completing the circuit. Lubricating the contacts and spring mechanics with a nonoxide grease reactivates the switch operation. Repair of the bimetallic blade control switch is limited to an adjustment in the temperature setting of the control to agree with the temperature recorded in the appliance or equipment being tested. Temperature of equipment should be tested by a reliable temperature tester or a good thermometer.

Repair of the helix control is limited to adjusting the temperature setting of the control to agree with the temperature recorded in the appliance or equipment being tested. If the control cannot be adjusted, the complete control assembly must be replaced.

If a timer fails to operate, use the following procedures to locate the trouble:

Test the electrical circuit for a blown fuse. Check for friction between the hands of the timer and timer crystal.

Check all wire connections.

To repair an inoperative electric timer, perform the following steps:

Replace the blown fuse with a fuse of the proper rating.

Replace the complete rotor if the rotor is inoperative. Replace the complete coil assembly if the field coil is burned out. Repair the timer switch assembly by cleaning contacts or reforming the contact arm to ensure positive contact. If the contact shows excessive wear, replace the switch assembly.

Adjust the hands of the timer if they are binding. Check all connections at the back of the timer for positive contact to ensure a complete circuit.

Elements can be checked using a -voltmeter or ohmmeter. If a voltmeter is being used remove one wire from the element and check for voltage between the empty terminal and ground. A voltage reading indicates a good element, and no voltage indicates an open or defective element.

If an ohmmeter is used, first ensure that the power is disconnected. Remove both conductors to prevent a false reading. Connect the two leads of the ohmmeter to the two terminals of the element. A reading of zero indicates a good element. A reading of infinity symbol indicates an open element.