Decoding the Markings on Your Car Light Bulbs

Have you ever wondered what those markings on your car light bulbs mean? Understanding these markings can help you make informed decisions when replacing or upgrading your bulbs. This guide will demystify these codes and help you understand what they signify. So, let's explore the fascinating world of automotive lighting!

Manufacturer's Name or Logo 

First and foremost, you will find the name or logo of the manufacturer on the bulb. This information is crucial in identifying the brand and ensuring you purchase a quality product from a reputable source.

Voltage Ratings 

The numbers 6V, 12V, or 24V indicate the rated voltage of the bulb, as per the ECE (Economic Commission for Europe) Regulation 37. These numbers are essential in determining whether the bulb is compatible with your vehicle's electrical system. For example, a 12V bulb should be used in a 12V electrical system.

International Category Description 

Symbols like H1H4, H7, and P21W represent the international category descriptions of ECE-standardized bulbs. These codes correspond to specific wattages and bulb types, such as a 55W H7 headlight bulb for your vehicle.


Country of Approval 

The letter "E" followed by a number (e.g., E1) denotes the country where the bulb has been tested and approved. In this case, "1" represents Germany. This information helps identify the regulatory standards the bulb has been subjected to during the testing process.

DOT Approval 

DOT stands for the United States Department of Transportation. This federal entity sets the safety standards for motor vehicles and their components, including car light bulbs. If the bulb is marked with "DOT," it is approved for use in the American market.

UV-Reduced Bulbs 

According to ECE standards, the letter "U" signifies that the bulb is UV-reduced. These bulbs are specifically designed for use in headlamps with plastic cover lenses, reducing the risk of damage caused by ultraviolet radiation.

Approval Mark 

An approval mark granted by the appropriate authorities is inscribed on the bulb. It typically consists of a combination of numbers and letters, such as 37 R (E1) + a five-digit number or only (E1) + a three-digit number. This code provides information about the bulb's regulatory compliance and the testing authority, such as the Federal Department of Motor Vehicles in Flensburg, Germany.



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Manufacturer's Coded Mark 

Most bulbs feature a coded manufacturer's mark that allows for traceability back to the manufacturer. This information is essential for quality control and accountability.

Mandatory Markings 

Due to space constraints on some bulbs, the legislator requires only the following obligatory information to be displayed: Manufacturer, output, inspection tag, and approval mark. These minimal markings ensure that critical information about the bulb is available to the consumer.

How To Choose the Perfect Car Light Bulbs

When shopping for car light bulbs, consider factors such as brightness, color temperature, and energy efficiency. The right bulb can enhance your vehicle's appearance and performance while helping you save energy and reduce energy costs. Whether you need headlight bulbs, tail lights, or interior lighting, understanding the markings on your car light bulbs will ensure you make the best choice for your vehicle.

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