Headlight Adjustmet "How To's"

[magwakeenercew2jh]

Doing some fine tuning last night on the new amber LED's in the instrument cluster had me driving down the road in the dark.

I don't like to drive at night. Never even did when I was a pup. It's waaaay worse now.

Last night was my first "in the real dark" drive since I put the truck together.
It was kinda like driving like the first pic attached.

I know where the up and down screws are on the headlight. Put 'em in myself.

But what do you folks do to get a good measure on the height and width?
Touch and go out on the street in the dark? Up against the garage at a certain distance? Or ??????

Thanks.

[TexasSteve]

The book says to measure it on a wall. But I go out on a deserted stretch of dark road (i live out in the country so it takes me about a minute to get there), park in the road, put my hazards on in case somebody does come by and start adjusting them. Getting in & out of the seat a few times for a visual reference instead of just looking at the pattern on the road. I just use a combination of vision from the seat & judging the light pattern on the road to set mine. Worked great on my 1987 Pontiac Trans Am GTA & only had my '02 GMC Sierra for 2 weeks now so I haven't touched it. I avoid night driving too, due to a wreck in '04 which affected my vision, so haven't even seen how the Sierra is for lighting at night yet.

[hayhauler71]

I use a headlight aimer that I got from work because the owner got sick of looking at it

[Stocker]

I aim horizontally so the high beams point straight ahead, and vertically so the low beams have maximum forward illumination without offending oncoming traffic. Simple, basic, and effective.

[truckster]

You need level ground, a wall, and a tape measure. You should also have a full tank of gas, but that will make more of a difference in a Blazer or a Suburban than a truck, because of where the tank is located.

At 25 feet from the wall, the top cutoff of the beam should be the same height as the top of your headlight. The left cutoff should be straight ahead of the left edge of the truck. The right headlight should meet the left headlight's right cutoff. That's about all there is to it.

[theastronaut]

The low beam pattern needs to drop 3" over 25 feet. If the beam pattern doesn't drop then ANY incline will make your headlights shine up into oncoming traffic. Measure from the center of your headlight to the ground, and subtract three inches. Find a level spot and park 25 feet from a wall, then mark the wall at that height with masking tape. Has to be very level since you're only dealing with a .60 degree angle. The top of your low beam pattern needs to be just under the tape line. If you have sealed beams than the light pattern will be a "blob" of light that can make aiming more difficult- there won't be a defined line where the upper half of the low beam pattern stops off. If you have H4 headlights that are E-code, you'll have a sharp cut off on the top half of the low beam pattern that makes aiming easier.

Here's a diagram.




Here's a shot that compares the E-code pattern (left) to SAE/sealed beam pattern (right side). You can see that the E-code makes a sharper line for easier aiming, and less glare for oncoming traffic.