nun-1" Tools for Electrical System Trouble- Test Light Unpowered Test Ligm The unpowered test light consists of a 12-volt light fitted with two leads and some sort of clip or probe lor contact with electrical circuits. The leads are neither POSITIVE or NEGATIVE. so no polarity problems exist when using the unpowered test light How to Use the Test Light 1. Checking For Power. Connectone test lead to a good ground or the NEGATIVE terminal of the battery. Use the other lead to check lor power at wires. connectors or components When the lightcomes on. there is power at the location. Ehcking For Power with An Unpoweied Test lg I. 2. Investigating a Blown Fuse Condition: a. Turn off all sqmpment powered through the luse to be tested. b Disconnect all unswitched components powered through the fuse to be tested. . . ii a motor. unplug the connector. . if a light. remove the bulb. c. Turn the Ignition switch to RUN, it necessary. to supply power to the luse (to test equipment such as radios. windshield wipers. etc). o. Connect a test lead to the hot end of the blown luse and the other to ground. ll the light glows. there is powerto thefuse. Movethe grounded lead to the otherend oi the luse. lithe light stays OFF, a short in one ol the components on that luse is indicated II it comes ON. a short to ground in the wiring is indicated. 3. Locating A wiring Short To Ground. The sell-powered testlight is a lightand battery holder assembly litted with test leads. The light, battery and test leads are connected in series so that when the test leads are connected to two points on a continuous circuit. the light glows, How to Use the It a wiring ground is indicated, isolate Self- Powered Test the ground by removing the L- ht connectors in the oircmts one at a '9 time. As shown in the ligure below. with the ground at "x" the test light will go out when 01 or 02 is disconnected. However, the test light will stay on when CG is disconnected. This tells you the ground is between (3-2 and C-3. Remember. reconnect 1- each connector oelore testing the next one in sequence. FUSE woman my I IGHY Self-Powered Test Light Typical Sell-Powered Test Ligm CAUTION: Disconnect the NEGATIVE battery cable from the battery belore using the self-powered test light, Checking Clrcult Continuity. Connect a test lead to each end at the suspected circuit or, at least. over the segment oi the circuity where the currect flow is suspected oi being broken. ll the light remains OFF. the break is between the two test leads. To check a switch for continuity. lirst disconnect one ol the switch terminals to isolate it from the rest ol the circuit. Then operate the switch in all positions (in a multi-terminal switch you may have to check more than one terminal). if the light comes ON the switch is functional Connecllng SettF'owered Tesl Lighl Checking Ground. When a loss of ground or an unwanted ground is suspected. connect one light lead to the point in question and the other lead to a good ground. It the light comes ON. it shows that the pornt is connected to ground. II it remains OFF. the point is not connected to ground, Shoong Jumper Wire Jumper Wire A jumper wire is used for bypassing sections of a circuit or a component it temporarily bridge" an open circuit A jumper wire can be purchased or easi made. You can make several of different lengths for convenience when testing. To make yourown jumper cables, simply attach alligator clips to each end of a length at heavy wire (such as 16 gauge automotive primary wire) so that extra resistance wont be placed into the circuit, When you neec a probe tor momentary jumping". simply insertasmall nail into one ot the clips How to Use the Jumper Wire Checking a Switch CIrcult. Turn the switch to the ON position II the components do not begin to function. connect a lead to each terminal at the switch. it the component begins to function. a malfunction in the switch is indicated CAUTION: Do not use a jumper wire to bypass a high-resistance load such as a lamp or motor that is connected between the hot circuit and ground. This creates a direct short circuit and may cause personal injury. fire or otherdamage to the vehicle