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Headlight Wiring Diagram: Why is following a diagram for wiring headlights important?

If you are new to the industry, you are likely overwhelmed by the diagrams and stuff. So,  you think that headlight wiring is a very hectic task. 

When you start doing it, you will see that the headlight diagram makes the chore pretty much simple. You just need to learn how to read it. Let’s look into it.

Table of Contents

Why you should use a Headlight Wiring Diagram?

As you work with many small wires and components, the chances of mistakes are high. Moreover, one single move can make or break the circuit. Sometimes, the damage is beyond repair as well.

If you have a diagram, to begin with, then you will have a layout of how to execute the wiring process. Moreover, it also makes it easy to place the correct wire with the correct connector.

Additionally, many wiring diagrams come with step-by-step guidebooks or manuals so you can follow them while wiring and get the proper routing without any difficulty or major issues.

Using the correct guidebook, you can easily do the foolproof & perfect installation without any external help from mechanics. 

Outer View of Headlight After the Assembly

Caption: Outer View of Headlight After the Assembly

How to Read a Headlight Wiring Diagram?

Reading a headlight wiring diagram is an art; without practicing, you can’t master it. Initially, you will need the knowledge of symbols and what they are used for to simplify the task.

Here, you should remember that every manufacturer in the market has its symbolic representations or legends. But, they name the symbols in their style, i.e., alongside guides. 

Hence, first, get the insight of their specific legend and then start executing the work. 

Legends usually include:

  • Module code
  • Component abbreviations
  • Color coding for wires
  • System group codes
  • Additional notes 

Although different manufacturers follow different legends, their symbols may be similar. Hence, it won’t be difficult for you to switch from one type of product to another.

Common wiring components are transistor, fuse, light, power source, open/close switch, and grounding point. These symbols join with a single line, representing the wires. However, these lines can be colorful, showing which color wire will connect in a specific circuit part.

Many headlight upgrading companies have their schematic diagram available along with the legend. Don’t forget to check that out because, eventually, it will help you a lot!

Which diagram do you need for your vehicle?

Every car has its unique wiring schematic and requirements. How you have installed the headlight in one vehicle may not work in the next!

So it is wise to learn about the car and start working on it. You can get these diagrams on the manufacturer’s website. 

Headlight upgrades also have their wire diagrams with installation instructions manuals. So, if you purchase such a legend, look for the documents along with it.

custom fuse box wiring harness 

Caption: custom fuse box wiring harness 

How to wire a Headlight according to the diagram?

A wiring diagram may be something like this

A Typical headlight wiring diagram

Caption: A Typical headlight wiring diagram

Usually, there are two such connections: one is for the low beam, and the other is for the high beam.

It is recommended to follow the wiring from the battery to the ground and start connecting everything in between. That way, the wiring process will have a flow.

  • At first, it may look not easy to connect, but if you know the symbols, the diagram will get easier. 
  • Remove the battery ground terminal before starting the headlight replacement process.
  • You will also observe that there are fuses which then lead to the headlight switch, which has an automotive relay that links to the chassis for grounding.
  • Here, you will get the low-beam and high-beam wires and link them to their specific switch and connectors. 
  • Next, you will ground these connections by taking the wire to the car chassis. 
  • Then, you are done with the work.

Complex diagrams may confuse you as they can have an overwhelming amount of wire, switch, fuse symbols, etc. In such cases, just follow the path from the battery source to the ground, and everything will get easier for you (still, it’s recommended to check out the guidebook or Manual).


The headlight wiring diagram reduces the wiring work to half as it lays out a clear picture of what the wiring will look like at the end.

However, make sure that you have the correct wiring diagram to follow, which is in line with the vehicle you have.

At Cloom, we try to reduce your efforts toward the perfect wiring by providing a custom-designed wire harness. For more information, click here.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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