Where are the headlight adjustment screws located?
This blog will answer the following questions: Where are the headlight adjustment screws located? How to perform the headlight alignment? What are the different types of headlights used in passenger cars?
Where are the headlight adjustment screws located?
The headlight adjustment screws are located on top of the headlight housing. The engine hood must be open to access the adjustment screws. The location of the screws is clearly marked with arrows; in some cars, the screws are located behind the housing and require the disassembly of a few engine compartment panels.
Each lamp unit has a minimum of two adjustment screws, one screw adjusts the bulb or projector on the horizontal axis and the other is on the vertical axis. Apart from manual adjustment, the headlights also consist of motors used for cornering illumination and actuation of high and low beams.
The headlight adjustment is checked during the periodic maintenance of the vehicle. Headlight adjustment is only required when either one of the lamp units is new or any suspension component like a shock absorber or top bearing is replaced.
After the adjustment, the zero position teach-in is performed if the headlight has a control unit. The control unit uses this position as a reset point, all the motors in the lamp unit are actuated and brought back to the zero point after each engine start.
The actuator motors are only present in vehicles with intelligent lighting systems. If there is a more conventional setup like halogen bulbs, then there are multiple filaments for high and low beams, and no motor or control unit is required for actuation.
How to perform headlight alignment?
The procedure for doing headlight alignment is given below and a headlight aligner or alignment tool is used to properly align the headlights:
- Park the vehicle on a level surface and check the tire pressure on all tires.
- If the manufacturer specifies to put 70 kg weight on the driver’s seat then add weight and keep the front wheels in a straight direction.
- Prepare the headlight alignment machine, and set the window of the headlight aligner at the level of the headlight. The distance between the headlight and the window should be 12 inches.
- Switch on the ignition and turn on the low beams, observe the light pattern in the window of the headlight aligner.
- The light pattern should not be above the horizontal axis, which will mean the high beams will be pointed towards the sky.
- The vertical cut-off should be visible on the target in the window of the headlight aligner.
- The light beam can be adjusted by turning the adjustment screws clockwise or anticlockwise.
- Repeat the procedure for both the headlights.
After the adjustment is completed, park the vehicle 20 feet from a wall and check the light from both the headlights. It should be on the level and the left and right high beams must not be further apart.
If the vehicle has a hydraulic or pneumatic suspension system then a dedicated vehicle level sensor is present on the rear axle. The headlight control unit also uses the data from the ride height sensor to change the low beam level if the vehicle is fully loaded or there are undulations on the road.
If a multi-function camera is present behind the windshield, the high beams automatically lower if light from oncoming traffic is detected. Therefore there is no need to adjust the high beams on the vehicles with an intelligent lighting system.
Many premium car makers like BMW, Mercedes Benz, and Audi also have an option to convert the headlight from left-hand side traffic to right-hand side traffic if the vehicle is driven in a foreign country.
Otherwise, the driver-side headlight is masked to prevent headlight glare on the on-coming traffic. The headlight adjustment screw cannot lower the high beam far enough in such vehicles.
What are the different types of headlights used in passenger cars?
The different types of headlights used in the passenger car are given below:
- LED lights
LED lights are more popular in the latest cars as the power consumption is very low and manufacturers can use intelligent lighting systems like curve illumination and glare protection. The LED can also be packaged in a very small space, there is no requirement for huge reflective surfaces to focus the light.
LED headlights provide 5000 to 6000 lumens per light; they are one of the brightest headlights available in passenger cars. Adjustment screws are provided on the top of the lap housing as the rear side houses the control units and fans required to control and cool the LEDs.
- HID lights
HID, also known as projectors or high-intensity discharge lights, provides better illumination compared to halogen bulbs. There is no heating filament in the bulb, an inert gas is present in a bulb and an arc is created with the help of a ballast.
HID lights require a projector lens to better focus the light emitted from the high voltage arc in the bulb. Any standard HID bulb will generate 3000 to 5000 lumens per light although aftermarket bulbs can produce more bright light than standard bulbs.
The headlight adjustment screws are located on the top of the housing similar to the LED headlights. On the back, there is a maintenance cap that is opened to replace the HID bulb. There is a dedicated headlight water spray system to cool and clean the headlight lens.
- Halogen lights
Halogen lights are the most common type of headlights in passenger cars. The bulbs are mainly H4s and there is a separate filament for high and low beams. Headlight adjustment screws are present on the rear of the lamp housing.
It can be difficult to gain access to the adjustment screws but the halogen headlights don’t require headlight alignment as frequently as the other types. There is a headlight washer jet that is used to cool down the headlight unit as halogen bulbs produce heat.
The replacement cost of the bulb is the cheapest when compared to the HID and LED headlights. However, if the Lamp unit is old; the internal wiring may be damaged due to the excessive heat and long hours of operation.
It is not possible to repair the wiring and the complete headlamp unit is replaced along with the halogen bulbs.
This blog and the question about where are the headlight adjustment screws located explained the procedure to perform a headlight alignment. Even if a headlight alignment machine is not present, the lights can be temporarily adjusted by checking the high beam pattern on a wall. There is also a 4 to 5-level manual adjustment provided inside the headlight that can be adjusted from a switch on the dashboard.