Shining, THE

Illuminating facts about tow-vehicle headlights

ALL OF US WHO TRAVEL AT NIGHT HAVE seeN ONCOMING headlights that shoot right into our eyes, momentarily blinding us and perhaps sendine us into a spree of obscenities and a flashing of our own vehicle s bright lights. Traffic death rates are three times greater at night than during the day, according to the National Safety Council (NSC). The NSC also says driving at night is more of a challenge than many people think, as 90 percent of a driver's reaction depends on vision, and vision is severely limited at night. Depth perception, color recognition and peripheral vision are also compromised after sundown.

Add in the age factor - a 50-year-old driver may need twice as much light to see as well as a 30-year-old - and the importance of properly adjusted headlights is even greater.

OFFENDER OR STATISTIC

ONE WAY TO KEEP FROM being an offender or a statistic is to make sure your tow vehicle s headlights are properly adjusted, both unhooked and when there's a trailer in-tow - even if the weight-distribution bars are cinched up.

A specialized auto-repair shop or dealership can adjust a vehicles headlights or, if you are on a tight budget and are handy with a screwdriver or vehicle-specific adjusting tool and tape measure, you may prefer to adjust them yourself.

If your tow vehicle s headlights are marked with a VOL, VO, or VOR on the lens, they can be aimed visually. If they aren't, you'll be best off having a shop make the adjustments with special aiming equipment.

Provided you have visually adjustable headlights, there's a specific method for making the proper adjustments. It takes a little time. But the end result is that your tow vehicle will be safer for you to drive - and for those whom you meet coming the other way.

seeING SAFELY

UNITED STATES GOVERNMENT standards measure the headlight adjustment at a point only 25 feet in front of the vehicle, and allow a tolerance of about 4 inches in any direction from center.

A 4-inch error at 25 feet becomes a 4-foot error at 300 feet in front of the car. Three hundred feet is considered the critical point of illumination by safety experts who say a driver should be able to clearly see a person, an animal or a parked car at that distance with the vehicle's high-beams on.

With headlights aimed just 4 inches low at 25 feet you lose about 50 percent of your illumination, and those aimed 4 inches high can blind oncoming drivers. Hence the need for some accuracy in aiming headlights.

The adjusting procedure requires a level spot long enough to accommodate your vehicle (with trailer in-tow) plus 25 feet between your vehicle's headlights and a vertical wall. You'll also need a marker or tape, an appropriate adjusting tool to turn the headlight adjusters and something to cover headlights that aren't being currently adjusted.

For maximum effectiveness, make sure the tow vehicle and trailer are loaded just as you would during a trip: tow vehicle s fuel tank at least half-full, a driver and passenger in the front seats, and trailer water and LP-gas cylinders full.

When everything is ready, pull the tow vehicle up to the 25-foot line so its headlights are aiming squarely at the wall and the headlight lenses are right over the line.

BY THE BOOK

NOW COMES THE FUN PART. Measure the distance from the "axis" of each headlight to the ground and write it down. (The axis of the lamp may be determined by a dot, a cross or a bulbtype designation or name brand, or it will simply be directly in front of the bulb.)

You also need to find the center of the tow vehicle. This can be done by locating a hood piece or some other visual cue, or better yet, by measuring the distance between the axes of the two headlights.

If you are using the two corresponding headlights, low to low or high to high, split the distance in half to get the distance from one headlight to the center of the vehicle. Write this number down.

Now that you have the height of the headlights and the distance of each headlight from the center of the vehicle, walk up to the wall and put a mark or piece of tape on it that represents those measurements.

Draw or tape a horizontal line through all of these points, and then draw a vertical line through each of the points extending about 4 inches below the line just drawn. This sets up your aiming-point references.

If your headlights are marked VOR or VO you are ready to adjust your lights, otherwise you have to draw a second reference line.

For VOL headlights, mark off 2% inches below the original horizontal line at a couple of places, dien draw a second horizontal line through these points.

The marks or tape on your wall should now look like one of these figures below if you have VOL headlights (VO or VOR lamps will have only the top horizontal reference line drawn.)

MAKING THE ADJUSTMENTS

NOW YOU ARE READY TO AIM THE headlights. Cover or disconnect the lights not being worked on while aiming one light. Put lights on low-beam.

Open the hood and locate the adjustment screws. On most models they will be easy to find, typically located on the top of the headlight housing. Some may be a little harder to find, even hidden, but they will be part of the headlight assembly.

On pre-1990s model trucks and SUVs the adjusting screws will probably be Phillips-head. On later model vehicles (with composite lights), its a little more complicated. For example, 2002 and up GM adjusters are a size 15 Torx, a common size. Late-model Fords, on the other hand, use a less common 4MM socket for their adjusters.

You'll note many modern headlight beams have a vertical cutoff at the top of the pattern that slants up on the right side.

Use the adjusters, one headlight at a time, to line up the flat part of the cutoff with the lower line if your lamps are VOL. Line it up with the top line if your lamps are VO or VOR.

Once the low beams are adjusted on dual filament bulbs, it's time for the high beams.

If your tow vehicle uses a four-light system, the high beams are adjusted with the bright spot centered on the intersection of the vertical headlight axis mark and the same horizontal reference line used for the low beam.

Some newer vehicles only have one adjuster; others have them for horizontal and vertical adjustments.

Adjustments on the vertical axis are the easiest and more important, but if your lights point to the center of the road, they should be brought back to center.

That's adjusting the headlights by the book. There's another, more rudimentary way that this can be done if time and space aren't in your favor.

RUDIMENTARY APPROACH

IF YOUR TOW VEHICLE'S HEADlights are properly adjusted from the factory, you can use a level and a tape measure instead of a wall to make basic adjustments.

With the vehicle level, measure the distance from the ground to the center of the headlight axis. You can do this by using a level to extend out from the mark that designates the headlight's axis to the tape measure. Note the height the level crosses on the tape when the level's bubble is centered. This is the distance from the ground to the axis ofthat headlight.

Now, when the tow vehicle is laden with a trailer, re-measure the distance from the ground to the headlights using die above method.

If the new measurement shows the headlights are "high," use the headlight adjusters to bring them down to their non-towing level. This should bring the headlights back to a safer adjustment.

You can also note how many "turns" you made on the adjusters so that when the trailer is disconnected you can readjust die headlights without using the tape and level. Noting how many turns of the adjuster are made can also apply to the by-the-book method.

UPGRADING HEADLIGHTS

PERHAPS YOU ARE CONSIDERING upgrading your tow vehicles lighting system with an aftermarket version. There are three types of lights on the market that arc worth considering: High-intensity discharge (HID) headlights, xenon/halogen headlights and conventional driving/fog lights.

HID lights produce more light with less wattage and heat than any other lighting systems available for vehicles. These are the "blue tint" lights that you see on more expensive automobiles and are pretty much the same as the sodium and mercury vapor lamps that light many streets and parking lots.

IiIDs are said to be far superior to the halogen headlights found on the majority of todays pickups and SUVs.

For quite a while HID lights were for low beams only on single-headlight vehicles. Recently, however, new versions of HID lights have been developed that use a mechanical screening device to enable one arc to produce high and low beams.

But they are not without disadvantages. HID lights have a very sharp "cutoff line that causes a lot of glare to oncoming drivers when the road is bumpy and the beam is bouncing up and down.

Another disadvantage is these lights are powered by a ballast. Finding a place to put them on a vehicle that wasn't designed with ballast placement in mind can be a challenge at times.

They are also expensive. Most cost hundreds of dollars for a set and can go well over a thousand dollars - not including installation costs.

Another, less expensive option is the xenon/halogen lighting system. This light replaces the traditional halogen light with a bulb that is charged with a mixture of high-pressure xenon and halogen gas.

Xenon/halogen lighting systems put out more light that is whiter in color than regular halogen lights. (Experts say the whiter the light, the better the visibility.) These lamps can be purchased for around $50 a pair and directly replace the factory bulbs. If you choose super-white lights, two excellent choices are Sylvania Silver Star or Philips Vision Plus. For vehicles with SAE standard sizes, like many base-model and older trucks, a European code headlamp with a replaceable quartz-halogen bulb can be swapped in.

A word of caution: There are many lights out there that claim to be super white, but are cheating by using excessive wattage to attain their extra-white light, or even special filters to create the look of the more expensive lights.

Any wattage greater than that allowed for in stock lights imperils your lighting system. High-wattage bulbs can easily overheat wiring looms, connectors and electrical circuits. They can also damage the plastic light housings themselves.

Other super-white lights use filters to get a white or bluish light. Such filters may actually reduce the amount of light thrown in front of the driver, reducing visibility.

Once you have your tow vehicle s light set up, you can rest assured your own safety and those of on-coming drivers is maximized.

Copyright T L Enterprises, Inc. Mar 2005
Provided by ProQuest Information and Learning Company. All rights Reserved