How to Wire Fog Lights With Vehicles

by Contributing Writer; Updated June 12, 2017

Fog lights are yellow to prevent glare. They should not to be confused with driving lights, which are extremely bright and reduce the vision when on in a condition with fog. Fog lights should be mounted as low as possible. Many year Vehicles have pre-existing holes drilled Vehicles driving or fog lights as an accessory. If not, a location should be found with ease of mounting and in a desirable low location in mind. When purchasing fog lights, get a product that comes with an inline fuse, a relay and a switch, all of which are needed during installation. If Vehicles some reason yours do not come with the kit, purchase the other parts Vehicles the same time.

Under The Hood:

 How to Wire Fog Lights With a Relay

Disconnect the negative cable from the battery.

Use a self-tapping sheet metal screw and mount the 10 amp circuit breaker in a location near the battery. Good places to mount the circuit breaker are the inner fender or the radiator support.

Mount the relay in the same area as the circuit breaker, also using a self-tapping screw.

Run a 14 gauge wire from the fog lights to terminal 86 on the relay. Connect this wire to the pigtail of the fog light with a solderless butt connector and to the relay using a solderless female spade connector.

Connect a short wire from terminal 85 on the relay to terminal 87a. Make your connections using solderless female spade connectors.

Mount a SPST toggle switch in an area easily reached by the driver. Connect a wire to the center terminal on the toggle switch using a solderless female spade connector. Run this wire to a metal part of the under dash area. Use a self-tapping screw and a solderless ring terminal and attach this wire to the metal. This needs to be a good connection, so make sure that there is no paint under the terminal.

Run a wire from the toggle switch to relay terminal 30. Use solderless female spade connectors on both the switch and the relay.

Connect relay terminal 87 to one of the circuit breaker terminals. This will require one solderless female spade connector and one solderless ring connector.

Connect the other terminal of the circuit breaker to the positive terminal on the battery.This will also require one solderless female spade connector and one solderless ring connector.

Reconnect the negative battery cable.

Items you will need

  • Fog lights

  • Automotive relay such as a Signal Stat 192

  • Solderless insulated female spade terminals

  • 10 amp automotive circuit breaker

  • SPST toggle switch

  • 14 gauge primary wire

  • Solderless butt connectors

  • Solderless ring connectors

  • Self tapping screws

  • Solderless connector crimping tool

  • Wire cutters

 How to Wire Fog Lights on a GMC Sierra

Install the fog lights in the desired location with the provisions in the kit. Install a piece of 10-gauge wire with a yellow butt connector to the black ground wire at the fog light and attach it to a good ground on the frame with the yellow oval connectors.

Disconnect the negative terminal on the battery. Attach the relay in an easy access location as close as possible to the fuse and relay center on the driver's side fenderwell. Attach a piece of 10-gauge wire from the battery main input wire at the fuse and relay center to the 30-amp in line fuse and from the fuse to the fog light relay B+ terminal using a yellow oval at the fuse box and a yellow female blade at the relay.

Attach another piece of 10-gauge wire from the relay to the fog lights using a yellow female blade at the relay and t-ing both fog lights into a yellow butt connector. Attach a 16-gauge wire with a blue female blade to the ground side of the relay and to a good ground using the blue oval connector.

Attach a 16-gauge wire from the last terminal on the relay through the firewall to the switch using the blue female blades. Locate a straight blade terminal on the driver's side fuse block that has power only when the lights are on. Use the voltmeter to check for power. The harness from the headlight switch can also be used. Once a terminal or wire is found that has power only when the lights are on, attach a 16-gauge wire from there to the switch. Reconnect the battery negative terminal. Now the fog lights will only turn on when the headlights are on. They can be turned on or off as long as the main lights are on. When the headlights are off, so are the fog lights.

Items you will need

  • Drill and assorted drill bits Phillips screwdriver Wire crimping tool Set of wrenches Voltmeter 4 standard yellow female blade connectors 2 yellow oval butt connectors 3 yellow butt connectors 2 blue oval connectors 2 blue female blades 2 blue butt connectors

 How to Wire Up Fog Lights to BMW E36

Open the hood and locate the backs of the fog lights in the front of the engine bay. Insert a narrow tool like a screwdriver through the hole that's adjacent to the fog light housing. Push the screwdriver against the clip that holds the fog light in place to release it. Make sure the fog light does not fall out when you release it.

Cut the wire of the new fog light bulbs so there are about two inches left.

Remove the OEM bulb from the fog light housing and cut the wires to the bulb, leaving the wires on the inside of the bulb connector.

Solder the wires from the inside of the bulb connector to the new bulbs. Cover the wires with electrical tape or heat shrink. Reassemble the fog light.

Cut the wires on the ballast that lead to the bulb if the new lights come with a ballast.

Cut the OEM fog light connectors of the car, leaving enough wire to work with.

Solder the ballasts to the fog light connectors on each side of the car, paying attention to the colors of the wires. Cover the wires with tape.

Hook up the new connections and check to make sure that the fog lights turn on.

Items you will need

  • New fog light bulbs

  • Screwdriver

  • Electrical tape of shrink wrap

  • Soldering kit