Fog Light Wiring and Connection Diagram with Relay and Switch


The fog light is a very important part of the lighting system on a vehicle or car. Normal headlights are useful for a normal night time but when the season is bad means the rainy season or winter season creates so much difficulty to properly see or navigate. Here the fog lights help a lot. A fog light is also called a driving light. The fog light is must need to install in the car at the right place. Basically, it is good to place the fog light at just the center of the vehicle, and the distance between the two lights are should be an equal distance from the side and the center of the vehicle. Also, it is to be kept in mind during the installation that it should not block the other lights such as regular headlights, marker lights or not block the coolant airflow, etc. So the connection and placement both are very important factors when installing the fog lights. It should be done very carefully to avoid any serious failure.

Now come to the connection procedure. Fog light can be connected with a relay or without relay, When you connect it without relay you will need some wire splicers. But in most of the cases, it is connected with a relay. So we will see the connection diagram with a five-pin relay. When it is connecting with the relay, then also two methods are followed - one is positive triggered and another is negative trigger. In the positive triggered circuit, the positive terminal is connected to the relay whereas in the negative triggered circuit the positive terminal is connected to the relay. Positive triggered is the most convenient.


Fog Light Wiring and Connection Diagram


So, first of all, let's see the wiring and connection diagram of Fog Light with Relay, Battery, and Switch.

Fog Light Wiring and Connection Diagram


Here, you can see we have used two fog lights each of them has 35 watts. So the total load is 35 + 35 = 70 watt. And we have used a 12 V battery. As it is DC so the current flow will be 70watt/12V = 5.8 A. It is better to use a wire that can handle at least double current of the actual current of the circuit. So, if your apparatus is the same as mine, you must use a minimum of 14 gauge wire that can handle current up to 12A.

Also, you can see in the wiring diagram, we have used a fuse in series with the battery. It is best to use a fuse that has a current rating of 80% of the wire's current capacity. So, in this case the 10A fuse is perfect.

Let's the details of the component we have used,

Fog Light - Each of them is 35 watts and has two terminals - a positive terminal and a negative terminal.

Battery - Battery supplies 12V DC power supply

Switch - Here we have used a Single Pole Single Throw(SPST) Switch that has two terminals for the connection and it has only the On and Off operation.

Indicator Lamp - It is connected after the switch, it will indicate if the fog lights are on or off condition.

Relay - Here we have used a five-pin relay that has five pins or terminals named as 86, 30, 87, 85, 87A. 85 and 86 are the coil terminals and the 30, 87, 87A are the contact terminals.


Connection Description
  • Negative terminals of all devices or components are connected to the ground means vehicle metal body or chassis. The connection of the negative terminal to the ground should be done correctly and properly otherwise it will not glow properly.
  • The positive terminal of the battery is connected to pin no 30 of the relay through a 10A series fuse.
  • Pin no 87 of the relay is connected to the positive terminals of the fog lights.
  • Pin no 86 of the relay is connected to the ground.
  • Pin no 85 of the relay is connected to the SPST switch.
  • Another terminal of the Switch is connected to the fuse box and the fuse box is powered by Battery Power or IGN.
  • The positive terminal of the indicator lamp is connected to the output of the switch and the negative terminal is connected to the ground.


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Fog Light Wiring and Connection Diagram with Relay and Switch Fog Light Wiring and Connection Diagram with Relay and Switch Reviewed by Author on 3/06/2022 Rating: 5

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