Whether you're cruising the PCH at night or just need to see through the coastal fog to get to work, your safety depends on your headlights. Here's what you need to know about how your headlights work, how they can be damaged, and what you need to do when you replace them.
Types of Headlights
- Halogen bulbs are a relatively recent addition to household lighting, but they've been used in automobiles for decades. These lights use a tungsten filament surrounded by a glass bubble filled with halogen gas that helps increase light output as well as durability. Older vehicles combined the lens and bulb into a single unit; this design is still used for some work vehicles like a few versions of Ford's Heavy Duty trucks. Other modern vehicles use a small bulb that mounts inside of a reflective housing or sits behind a projector lens.
- High Intensity Discharge (HID) bulbs are sometimes called “Xenon” bulbs due to the use of the gas inside the bulb. This lighting technology uses a combination of rare metals and gases to create an intense bright light. These bulbs provide as much as three times the light of a halogen bulb, but this light must be carefully managed to keep these bulbs from blinding other drivers. To achieve this, HID lights typically use a projector-style housing and have other features like self-leveling to keep the correct aim. Like the fluorescent bulbs used in offices, HID lights also need a ballast to regulate current.
- Light Emitting Diode (LED) lights are far more efficient than halogen or HID bulbs, and they have an incredibly long life, often being able to last as long as the vehicle if they aren't damaged. They were first used in tail lights because they light up faster than other bulbs, increasing the time other drivers have to react. LED headlights are close to HID lights in brightness, but they're more efficient, reducing the electrical load, and they allow more options for headlight shapes, opening up styling options for designers.
Why Do Plastic Lenses Get Foggy?
A plastic is a polymer, which is essentially a really big molecule made up of long, continuous chains of atoms. As UV light passes through, it can break some of those bonds. Break enough bonds and the plastic weakens, losing its strength and translucency, leading to yellow, brittle lights. While the plastics used in headlight lenses have high levels of plastic stabilizers to prevent this, any plastic will break down when exposed to enough UV radiation. The plastic itself is also softer than glass, so the surface is scraped up more easily by road debris. However, it also resists impacts better than glass and doesn't leave dangerous shards on the road after an impact.
How Does Water Get Into Headlights?
Headlights come sealed to protect the bulbs and reflectors from dirt and water. A tiny crack in the housing or lens can let water seep inside, and since there aren't any drains, there's nowhere for that water to go. Cracks and holes in the lens can lead to faster water collection because they're in the path of the air going around the vehicle. That means if you're driving 75 mph on the highway, water is being forced into the crack at that speed.
How Do I Get My Headlights Working Correctly After They've Been Damaged?
While there are polishing kits available to return the clarity to your headlights' lenses, the effects are short lived due to the age of the plastic. For any other type of damage, there's not much you can do except replace the entire headlight housing. Original Equipment Manufacturer (OEM) headlights are far superior to their aftermarket counterparts because they have to meet the same quality and performance requirements as the lights originally installed in your vehicle. They also use the same styling and design, so if you replace just one headlamp, both lights will look the same and create the same lighting pattern.
How Do I Aim My Ford's Headlights?
Headlights should be aimed when first installed and re-aimed occasionally to adjust for changes in ride height as the suspension lowers due to wear. Headlights should be adjusted with the gas tank half full, the tires aired up to the correct pressure and someone sitting in the driver's seat. This provides the most accurate position for a range of driving conditions.
As mentioned earlier, some headlight designs have an auto-leveling feature and don't need to be manually aimed. For other designs, there are typically two screws on the back of the headlight mount: one screw mounted at the top of the housing changes the vertical angle, while another screw on the edge of the housing closest to the outside of the car changes the horizontal angle. Some lights may not have the horizontal adjuster, but a shim can be used on one of the mounting screws to bring the light in line if the angle is out of adjustment.
On some Ford models, there are a pair of bubble levels marked either in degrees or with a colored stripe indicating the optimum position. The adjustment screws should be turned until the bubbles line up with the “0” degree mark or stripe.
If you have adjustable headlamps without built-in levels, find a flat vertical surface like a wall or garage door and make sure there isn't any outside light that will make the beam pattern difficult to see. Get the car close to the surface and lay down a line of tape going from the ground up at the center of the vehicle. Turn on the low beam lights and look for a small dot in the light pattern. Run a line of tape horizontally through these dots.
Back the car up 25 feet. Measure the distance between the brightest part of the light and the vertical stripe. Turn the headlights' horizontal adjusters until the beam pattern is at an equal distance to this stripe. Next, adjust the vertical position until the brightest part of the light is on the horizontal tape stripe.
Where Can I Get Quality OEM Headlights for My Ford?
JimVreelandFordParts.com carries genuine factory Ford parts ranging from headlights to hood latches. Our site lets you search by VIN number and model information as well as part numbers and keywords like “headlamp” so you can quickly find the right headlight for your vehicle. Not sure if your Ford came with halogen or HID headlights? Have other questions about parts? Contact us to talk to our staff of factory-trained parts people.