How to Install Fog Lights with a Switch | BLIAUTO Professional Lighting Guide

In daily driving, fog lights serve as important auxiliary lamps, providing a wider and closer range of illumination in low-visibility conditions such as rain, fog, snow, or dust. Compared to the direct beam of regular headlights, fog lights use a lower angle and a wider, scattered light pattern, effectively reducing glare from light reflection and making the road and surroundings clearer.

Many vehicle owners choose to install fog lights with an independent switch when their cars either lack factory fog lights or when the original ones are unsatisfactory. This setup allows fog lights to be turned on independently, without being limited by the factory headlight logic, offering more flexibility in use.

Today, BLIAUTO brings you a complete fog light installation and switch wiring guide, helping car owners and modification enthusiasts install fog lights step by step.

1. Why Install Fog Lights with a Switch?

Enhanced Safety

In low-visibility conditions, fog lights effectively illuminate the nearby road and roadside areas, preventing missed obstacles, pedestrians, or curbs.

Flexible Operation

An independent switch allows the driver to turn the fog lights on or off freely, without relying on the headlight control logic, offering more convenience.

Suitable for Multiple Vehicle Types

Whether it’s a sedan, SUV, pickup, or motorcycle, fog lights can be easily installed with proper mounting and wiring.

Appearance and Personalization

The design and light color of fog lights can enhance the vehicle’s visual appeal. Especially with LED fog lights, which offer high brightness and a long lifespan, they are a popular choice for vehicle customization.

2. Preparations Before Installation

2.1 Tools and Materials

Before installation, it is recommended to prepare the following tools and components:

Phillips and flathead screwdrivers

Wrenches or socket tools

Electrical tape / heat shrink tubing

Wire stripper and crimping pliers

Power and ground wires

Relay (recommended 40A or higher)

Fuse (10A–15A)

Independent toggle switch or push-button switch

Fog light assembly (LED or halogen)

Mounting brackets and screws

2.2 Confirm Installation Location

Most vehicles have pre-made fog light mounts on the front bumper. If not, universal brackets can be used to mount the fog lights under the front bumper.

2.3 Electrical Plan

The wiring logic for fog lights with a switch generally follows this flow:

Battery positive → Fuse → Relay → Fog light positive

Fog light negative → Ground

The switch controls the relay coil circuit to turn the fog lights on or off

3. Step-by-Step Installation

Below is a guide for adding fog lights to a car, divided into fog light installation and switch wiring.

(1) Mounting the Fog Lights

Remove bumper or blank cover

Use a screwdriver to remove the panel covering the fog light position.

For modified vehicles, cutting or adding brackets may be needed for mounting.

Secure the fog light assembly

Place the fog light into the opening and fix it securely with screws or brackets.

Ensure the light is correctly oriented, neither too high nor too low.

Connect the fog light wiring

Each fog light generally has two wires: positive to the relay output and negative to a metal part of the vehicle body (ensure good contact).

(2) Switch and Wiring

Relay and fuse connections

Connect battery positive → fuse → relay terminal 30.

Relay terminal 87 → fog light positive.

Fog light negative → vehicle ground.

Switch wiring

One side of the switch connects to battery positive (or ACC power), the other side to relay terminal 85.

Relay terminal 86 connects to vehicle ground.

When the switch is closed, the relay activates, completing the circuit and lighting up the fog lights.

Switch mounting location

Common locations: pre-set dashboard switch slots, under the center console, next to the steering wheel, or near the driver’s seat.

If no suitable location exists, a standalone drilled switch can be used.

(3) Testing and Adjustment

First power-on test

Check that all wiring is secure, and wrap with electrical tape if needed.

Insert the fuse, turn on the switch, and ensure the fog lights work correctly.

Adjusting beam angle

The fog light beam center should not exceed the upper edge of the front bumper to avoid dazzling other drivers.

4. FAQ

1. Is a relay necessary for fog lights?

Yes. Fog lights draw significant power. Directly controlling them with a switch can burn out the switch or overload the circuit. The relay isolates and protects the switch.

2. What fuse rating should I use?

A single fog light typically consumes 30W–60W. Two lights together draw about 5A–10A. Use a 10A–15A fuse to prevent circuit damage.

3. Can the switch be connected directly to the fog light?

Not recommended. Direct connection can burn the switch due to high current and lack of relay protection, reducing safety.

4. Can fog lights be left on all the time?

No. Fog lights are mainly for low-visibility conditions. Using them in clear weather may blind other drivers and may violate traffic laws.

5. Can halogen fog lights be replaced with LED?

Yes. LED fog lights are brighter, consume less energy, and have a longer lifespan. Installation is the same as for halogen lights.

5. Installation Precautions

Keep wiring organized: Use protective sleeves or zip ties to prevent wear from vibration.

Ensure reliable grounding: Connect the negative terminals to clean metal parts of the vehicle body to avoid flickering or failure.

Waterproofing: Fog lights are near the ground; use waterproof connectors or wrap connections with electrical tape.

Follow regulations:  Some regions limit fog light colors (white or yellow only). Ensure compliance with local laws.

6. Summary

Adding fog lights with a switch improves driving safety in adverse weather and provides more flexible control. The installation process mainly includes:

Mounting fog lights: Ensure correct position and angle

Wiring: Use a relay and fuse for protection

Switch installation: Choose a convenient location and secure wiring

With this guide, even inexperienced car owners can successfully install fog lights. As a professional automotive lighting manufacturer, BLIAUTO is committed to providing high-quality LED fog lights and expert installation solutions, helping every driver enjoy safer and more comfortable driving.