Learn about Automotive Light Bulbs

Learn about Automotive Light Bulbs

Believe it or not an automotive light bulb is an interesting subject. In this article we will review why some bulbs may look the same but are actually different. Also covered is the difference between automotive lamps used on older vehicles compared to the ones on the most modern cars and light trucks. Finally we’ll cover problems and solutions for bulbs that experience repeat failure and provide tips for making sure the right replacement lamp is chosen.

Light Bulb Sockets

When we talk about automotive lighting, there is a major difference between specialized headlight bulbs and the rest of the lamps that you’ll find on the vehicle which we will focus on here. Where you find a bulb you will find a socket that is responsible for holding it in place and supplying current and ground that facilitate the illumination.The light socket plays a major role and is often the cause of problems. First off, it’s the socket that can be specially formed to hold extremely unique bulbs that can prevent the installation of the incorrect lamp in that particular socket.

The sockets either provide spring tension or latches to physically hold the bulb against the electrical contacts. If this component becomes damaged, melted, corroded or the contacts loosen operation can become intermittent.In this situation replacing the lamp will not solve the issue. Melted and damaged sockets are common problems with daytime running lights on a lot of General Motors vehicles. Because of the high wattage and the extended on time, the plastic socket is unable to stand up against the generated heat. In this situation the socket and the bulbs should be replaced as General Motors supplies improved parts made with heat resistant materials that will hold up much better.

How the Light is Powered

This is the area that separates the bulbs in the past from the ones we have today. Depending on your age, you probably remember a glass bulb with a brass shell base. These types of lamps usually had one filament and one center contact powered by one wire delivering voltage when needed. The ground was often considered a case ground as the brass shell found ground through the socket that was mounted to metal automotive parts.

Since modern sockets and many body panels are made from plastic two wire bulbs are now the norm. In the case of a double filament bulb that may operate the parking light and the turn signals you could see three or even four wires going to the socket. When diagnosing an inoperative light the most likely cause is usually a burned-out filament within the lamp. When this turns out not to be the case diagnosis should begin with verifying power and ground at the contacts when that individual light is turned on.

How to Replace Automotive Bulbs

The method of replacement is closely related to the design and construction of the light assembly. These fall into two main categories. Some light assemblies have a removable lens, so the bulb can be pulled or twisted out of the socket. The other type that is more commonly found on domestic automobiles is a lamp assembly where the socket and bulb is removed from the back of the housing to facilitate replacement. In some cases, figuring out how to gain access to the back of the assembly is only half the battle. Different manufacturers use different tricks to lock the socket and bulb into the housing. Some have push in and twist releases where others have retainer rings that must be loosen before the socket can be twisted to release.

The main take away from this article is that it’s imperative to replace a failed automotive bulb with the exact same type. Forcing the wrong bulb into a socket can damage it and incorrect current draw can damage wiring or blow the fuse for that circuit. In a situation where you find yourself replacing an individual bulb, many times you need to dig further to find the root cause. As an example if you replace the left rear brake light once every six months and have never had a problem with another lamp on the entire car, something is wrong with the socket or housing for that brake lamp. Moisture can be dried and a housing resealed just as a loose socket can be replaced and poor connections repaired.

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