Bulb Check
You can findlight bulbsjust about anywhere you look around in your vehicle. They are in front of your car, under the hood, inside the glove compartment, under the trunk and next to the license plate. And once in a while, one or more of them may stop working. Usually, all you have to do is look for a broken filament or dark film under the glass housing to confirm that the bulb has indeed failed. Other times, though, it's hard to tell. For those times, here's a simple test you can do at home to confirm whether your car light bulb is still good.Identifying the light bulb electrical contactsOn some light bulbs, recognizing the electrical contacts is easy. Just look for the two legs that make contact with the corresponding electrical contacts on the connector. Other times, this is not too obvious.Bayonet basetype light bulbs, for example, come equipped with a cylindrical, metallic base, and one or two contact points at the bottom. In this case, the cylindrical base is the bulb's electrical ground, and the contact or contacts at the bottom are the power side. Light bulbs with two bottom contacts function as two bulbs in one. They are commonly used as parking and turning signal lights.Testing the light bulbNow that you've located your light bulb electrical polarities, it's time to test it. Open the hood of your vehicle. Connect a jumper wire to either one of the light bulb legs and the other end of the wire to the positive or negative terminal on your car's battery. Hook up another jumper wire to the other electrical contact or leg on the bulb and the other end of the wire to the other battery terminal. If it is good, the bulb should illuminate. Otherwise, replace it.Testing a bayonet base type light bulbTesting a light bulb with a bayonet base is done in the exact same way as the two legs or two contact points light bulb. In this case, though, the cylindrical base serves as one of your contact points. Your other contact point is at the bottom. However, if the bottom of the bulb has two contact points, you basically have two bulbs in one. The ground or base is shared by the two bulbs.First, you test one bulb by connecting one jumper wire to the base and the other end of the wire to one of the battery terminals. Connect another jumper wire to one of the other two contact points at the bottom, and the other end of the wire to the other battery terminal. To test the other bulb, you just move the jumper wire to the second contact point at the bottom. Keep the other jumper wire connected to the base or ground. Both bulbs-or filaments inside the glass housing—should illuminate in turn. If one or both filaments fail to glow, replace the bulb.Next time you have a hard time telling whether one of your car bulbs is good or not, use this simple test. If the bulb works fine during your test, you know the problem lies somewhere else on the electrical circuit. In many cases, all you have to do is remove rust or corrosion from thebulb's socketor make sure the wires that connect to the socket are firmly hooked up.
