SPECIFIC TROUBLESHOOTING

Electrical problems generally fall into one of three areas:

• The component is not receiving current.
• The component has failed and cannot use the current properly, if at all.
• The component is not properly grounded.

The electrical system can be checked with a test light and a jumper wire. A test light is a device that looks like a pointed screwdriver with a wire attached to it and has a light bulb in its handle. A jumper wire is a piece of insulated wire with an alligator clip attached to each end.

It should be noted that a test light will only show that voltage is present; it will not indicate the amount of voltage. Certain components will only function if a minimum voltage is supplied. If a more than a "yes or no'' answer is required during diagnosis, use a voltmeter. If this must be purchased, purchase a multimeter or volt/ohmmeter (VOM). These reasonably inexpensive tools include several scales for both AC (household) and DC volts as well as an ohmmeter for checking resistance and continuity.

If a component is not working, you must follow a systematic plan to determine which of the three causes is the villain.

1. Turn on the switch that controls the inoperable component.
2. Disconnect the power supply wire from the component.
3. Attach the ground wire on the test light to a good metal ground.
4. Touch the probe end of the test light to the end of the power supply wire that was disconnected from the component. If the component is receiving current, the test light will go on.

   NOTE: Some components work only when the ignition switch is turned ON.

   If the test light does not go on, then the problem is in the circuit between the battery and the component. This includes all the switches, fuses and relays in the system. Follow the wire that runs back to the battery. The problem is an open circuit between the battery and the component. If the fuse is blown and, when replaced, immediately blows again, there is a short circuit in the system which must be located and repaired. If there is a switch in the system, bypass it with a jumper wire. This is done by connecting one end of the jumper wire to the power supply wire into the switch and the other end of the jumper wire to the wire coming out of the switch. If the test light lights with the jumper wire installed, the switch or whatever was bypassed is defective.

   NOTE: Never substitute the jumper wire for the component, since a load is required to use the power from the battery.

5. If the bulb in the test light goes on, then the current is getting to the component that is not working. This eliminates the first of the three possible causes. Connect the power supply wire and connect a jumper wire from the component to a good metal ground. Do this with the switch which controls the component turned on, and also the ignition switch turned on if it is required for the component to work. If the component works with the jumper wire installed, then it has a bad ground. This is usually caused by the metal area on which the component mounts to the chassis being coated with some type of foreign matter.
6. If neither test located the source of the trouble, then the component itself is defective. Remember that for any electrical system to work, all connections must be clean and tight.