1991 GMC G2500 Headlamp Alignment Adjust Cost

A vehicle's headlamps (or headlights) serve to illuminate the road during nighttime driving and to make the vehicle more visible during daytime driving. The headlamp system includes a low beam used for normal driving, and a high beam that is only to be used when no other cars are present on the road. While cars of the past relied on round, sealed-beam lamps, modern vehicles feature headlamps with aerodynamic shapes and replaceable halogen bulbs. Some headlamps are powered with high intensity discharge (HID) bulbs that put out more light. These lamps are also known as "Xenon headlamps" and stand out by their bright bluish-white glow. Most headlamps need to be manually aimed or adjusted so that they focus at the correct point on the road ahead of the vehicle.

A headlamp incorporates a bulb placed in front of a reflector (or a series of mirrors) that projects a beam of light through a lens and directs the beam to the road ahead. Halogen lamps produce more light with less heat output than older incandescent bulbs due to the halogen gas injected into the bulb. HID, or “Xenon,” headlamps provide even more light by producing an electrical arc for illumination rather than a glowing tungsten filament. Headlamp adjustment involves a technician manually aiming the headlamps so that they focus in the correct area ahead of the vehicle. Some late model vehicles feature self-leveling headlamps that that remain level with the road regardless of the angle of the vehicle. Vehicles with "adaptive headlamps" use a motor to shift the focus of the lamp to follow curves in the road.

Symptoms of improperly or mis-aligned headlamps include poor visibility at night, blank spots on the ground ahead of the vehicle, or headlamps that light up the sides of the road or surrounding landscape (i.e. trees, sidewalks). If oncoming drivers tend to flash their high beams, the problem could be due to improperly aligned lamps pointing toward the oncoming traffic instead of toward the road ahead.

Improperly aligned or adjusted headlamps present a vehicle safety issue. Poor visibility - or lights that shine in the eyes of other drivers - are more than a nuisance. They are safety concerns that should be corrected as soon as possible.

There is no maintenance interval for headlamp adjustment. Headlight alignment should be checked if any symptoms are present. Alignment should also be checked any time a headlamp assembly is replaced, or if the vehicle has been in a front end crash.

Before checking if the headlamps are misaligned, a technician will first rule out any other causes of some of the symptoms. For instance, if poor visibility at night is the concern, deteriorated or foggy headlamp lenses could be the problem. So could low voltage from a bad wire or a weak alternator. If it appears that the headlamps are out of alignment, a technician will park the vehicle on level ground, facing a wall at a measured distance, and determine whether the headlamps illuminate the wall at specific locations. Lights that shine away from the correct spots will need to be adjusted.

To align headlamps in modern vehicles, a technician will often use the same method used during diagnosis: park the vehicle on level ground facing a wall that is marked at the proper locations for the headlights to shine. If a light shines outside of its parameters, the technician will turn a set of adjusting screws located on the headlamp assembly to bring it into alignment up and down, left and right. Many vehicles incorporate leveling meters on the headlamp assembly to aid in proper aiming. Older vehicles that did not incorporate levels, instead included mounting tabs on the outside of the headlights that articulated with a special alignment tool. A technician would use this special tool to make sure the lamp was level.

Proper headlamp operation and alignment is essential for vehicle safety. Have a qualified technician determine if the headlamps are out of alignment, or if there is some other cause for poor visibility.

The headlamp adjusting screws used to aim the lamps can corrode with time and lack of use. It is not uncommon for headlamp adjusting screws to freeze up or break during adjustment and need replacement. (In come cases the headlamp assembly might need to be replaced). It is also possible that a headlamp is not capable of being adjusted because surrounding components were damaged in a front end crash. Even a minor collision can bend or break headlamp mounting locations and prevent the light from being adjusted properly.

Someone with intermediate DIY experience can successfully align and adjust the headlamps on most vehicles if proper conditions are met (i.e. flat parking area with sufficient room for the operation). On some vehicles with auto-leveling or motor-driven headlamps, the repair should be left to a professional.