Car Doctor Q&A: Make Your Own Short Tester

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Electrical faults can be a nightmare, but following AAA Car Doctor John Paul’s advice, you can make your own short finder and figure out the source of your problems.

Q. I have a problem with my car, it blows the fuse for the cigarette lighter/12 volt outlet. When the fuse blows the radio and some of the courtesy lights stop working. So far all I have been doing is carrying a supply of fuses. How do I find the short circuit?

A. You can buy a short tester for about $40, but if you’re handy enough to look for the short, you’re handy enough to make your own short tester.

Take a sealed beam headlight and wire spade connectors that fits into the fuse slot. Wire the connector to each side of the headlight. When using this be careful your terminal ends don’t touch together in the fuse socket. What will happen whenever the circuit is energized the headlight will come on.

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Now do a little research and find out what the fuse powers. When everything turned off- the headlamp should be off. Now time to get to work, start with shaking and wiggling the wires that power the lights, radio and 12 volt receptacle, if the headlight comes on or flickers during your wiggle test you have found the short.

John Paul is public affairs manager for AAA Southern New England. A certified mechanic, Paul tests dozens of new cars each year and also hosts a radio show on AM 950 and 550.