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How To Adjust Semi Truck Headlights? (For 7 Popular Brands)

Driving any vehicle at night is hard if you do not have a headlight. And you mostly need it if you are to drive a semi-truck since it is bigger and requires more care.

The primary purpose of the headlights is to provide safety and visibility when driving at night and in extreme weather conditions, such as rain, hail storms, or even thick fog.

It is essential to keep the headlights of your semi-truck set at the right angle always. You must ensure that the beam pattern of your semi truck’s headlights complies with the legal requirements to avoid violation.

Thus, knowing how to adjust the headlights is one of the most important things you should learn when driving a semi-truck.

Here’s a Quick Answer on How to Adjust Semi-Truck Headlights:

To adjust a semi-truck headlight, look for the headlight assembly on the bottom of the headlight. Look for a slot in the hood-mounted splash shield. Using a screwdriver, adjust the screw clockwise to raise the beam. To lower it, adjust counterclockwise until your beam pattern is on the cut-off line.

How to Know if your Semi-Truck Headlights need Adjusting?

Practicing regular inspection on your semi truck’s headlights before hitting the road is one of the necessary things to ensure safety, especially for overnight driving.

Some indications that your headlights need adjusting are when the approaching vehicles on the other road lane start to flash their lights on you.

It means that your light blinds them even without you turning the high beams.

Another is if you see that the road ahead is too bright within only 20 feet, which signifies that the aim of the low beams is too low.

Headlight misalignment may happen more often without you knowing it, so it is essential to always check it before making the necessary adjustments.

Many things affect the proper alignment of the headlights. Here’s a quick pre-headlights adjustment checklist you can follow:

  • Remove dust, ice, or mud from the fenders of the headlights.
  • Wipe the headlight lenses using a soft cloth with non-caustic soap and water.
  • Unload the semi-truck and inflate tires according to their recommended air pressure.
  • Check the hood is closed and latched.
  • Check the springs for the presence of leaves.
  • Check the suspension and ensure proper adjustment on its height.
  • Check the assembly of the hood and hinge. Repair if damaged.

Always refer to this checklist every time your semi-truck undergoes a repair. It is most likely that there are affected areas in the semi truck’s mechanism that cause the misalignment of the headlights.

How Bright should Semi-Truck Headlights be?

Well-lit headlights seem to be the most ideal to use as they can illuminate any dark roads.

However, maxing out the brightness of the headlights will make you look inconsiderate of other drivers on the road and violate the local lighting regulation for trucks and semi-trucks.

So how bright should you turn on your semi-truck headlights at night? The safest will range from 2400 to 4000 lumens. 

To ensure your headlights are bright enough, energy-efficient, and safe to use, you should consider LED or HID.

But if you are already using the recommended lights, you may check if yours needs some cleaning. You can wipe the headlights’ surface because particles like dust, ice, or mist also cause the light to get cloudy.

How High up should Semi Truck Headlights be Aimed?

The top of the low beam of the semi-truck headlight should be aimed below the headlight lens’s center height.

You should also set the right headlight, or the one on the passenger side, higher to illuminate the road signs.

While the left headlight, or the one on the driver’s side, should be lower so you will not blind other drivers on the other lane of the road. 

How Far should your Semi-truck Headlights Shine While on a Low Beam?

The low beam headlights can reach up to 200 feet if you drive at 25 mph. The distance is equivalent to half a city block.

Low beams are more appropriate when a car approaches you on the opposite side of the road or if you are behind another vehicle within 200 feet.

Light beams are also safer and more convenient when driving under heavy rain, thick fog, or snow.

Steps to Calibrate or Adjust Semi-Truck Headlights

Adjusting semi-truck headlights from popular brands have slight differences. To avoid confusion, you can check the guide below:

How to Adjust Volvo Semi-Truck Headlights?

First, open the hood and look for the adjuster on the bucket’s lower inside. With a Torx screwdriver, adjust the headlight to the required position.

To lower the light, you can turn the adjustment bolt counterclockwise. To raise the headlight, you can turn the adjustment bolt clockwise.

Test them before driving out to ensure you get the right angle and brightness.

How to Adjust Peterbilt Headlights?

Establish a horizontal line of one inch on an aiming surface at the same height as a level surface of the optical center. Look for the cover lens. It is either marked with “VOL” or “VOR.”

Make an H-H line based on the measurements provided in the semi-trucks manual. Make a second horizontal line or the A-A line below the H-H line.

Use a 10 mm socket to level the beam pattern with the A-A line to turn the adjuster. Do the same for the opposite headlight.

Remember that Peterbilt semi trucks’ low and high beams move with one another. You can only adjust the low beams.

Once you change the low beams on the A-A line, ensure the high beams are level with the H-H line simultaneously.

How to Adjust Headlights on Kenworth?

To fix Kenworth headlights, ensure you have a 13 mm wrench or socket.

Open the hood, and you will see a black plastic shield with three tabs on the top of the inside of the fender. Look for the bolt. You may remove it, but it is not necessary.

Behind the bolt, you will see the headlight housing. Using the socket, turn the black piece on the bolt to adjust the high and the low beams.

How to Adjust Headlights on an International?

Adjusting the headlights of an International semi-truck looks similar to the previous brands listed here. T

The difference is that its under-hood needs to change vertically above the lamp, while the horizontal adjustment is on the right.

Also, instead of using a Torx screwdriver and a socket, you need to use a screwdriver for hex head screws.

How to Adjust headlights on a Freightliner?

The Freightliner headlights can be adjusted using a vertical adjustment screw. Ensure you aim the headlights 25 feet away from a wall to do it.

Open the hood, and look for the backside of the headlight housing. You will see an adjustment screw. It is either black or white.

Use a Torx head screwdriver (or other screwdrivers for the particular Freightliner semi-truck model). Turn the adjustment screw until its beam shines downwards on the wall.

Ensure that the headlight beam will touch the bottom-most part of the wall from 25 feet away.

How to Adjust Headlights on a Mack?

To fix the aim of your Mack headlights, you only need to look for the metal stud at the bottom of the rear. It is on the screwed assembly on the housing of the headlight.

You will need a 4mm or 5/32 hex socket, and try turning or adjusting it to the preferred beam position. Remember that you can only change the socket in an up and down direction.

How to Adjust Headlights on a Western Star?

Adjusting the headlight of a Western Star semi-truck is similar to how you calibrate Freightliner’s headlights.

You can adjust the headlight on the bottom part in a close hood. 

Using a Phillips #2 screwdriver, you can turn the screw clockwise to raise the beam while using a counterclockwise motion lowers it until you achieve the standard alignment.

How Much does it Cost to get Headlights Aligned?

The cost of headlight alignment will depend on the brand of your semi-truck, dealer, and the mechanic you choose to do the service.

But, on average, the headlight adjustment will cost around $25 to $60 for a professional service.

However, if your only concern is the headlight adjustment, it will only take the mechanic a few minutes to fix. You will only then pay the minimum amount the local shop charged.

Therefore, it is essential to learn how to adjust the headlights. You will then save a couple of bucks if you need only a simple repair.