Vehicles without existing fog lights
Installing fog lights on a vehicle that doesn't have them already is trickier than replacing old fog lights. You'll have to add some wiring yourself, and you may have to drill a hole for the lights. Luckily, most vehicles today already have fog lights.
Firstly, you'll need to run wires for the on/off switch into the vehicle. The wires will go from inside the hood to the interior of the vehicle. Most vehicles already have a hole you can run these wires through. If there is no space, you may have to drill a small hole yourself.
Wiring the fog lights
Whether your vehicle already has fog lights or not, you'll have to connect several wires. Check the instructions that came with your fog light kit to ensure you know where each wire goes. Typically, there will be one power wire that connects to the on/off switch - this goes through the firewall hole, or the hole you drilled previously.
There will also be a ground wire. One end of this connects to the grounding terminal and the other end needs to be connected to an unpainted metal section of the vehicle under the dash.
Your fog lights will have a third wire connected to the fuse. One end of this wire connects to the on/off switch. The other end goes into the hood area and connects to the relay and the battery. This should be the last piece that you connect.
Installing lights into the bumper
Most vehicles have a place in the bumper for fog lights. You should be able to detach the bumper and install the new fog lights directly into the bumper. This can be easily done by unscrewing the bumper and removing it.
If your vehicle doesn't have an opening for the fog lights, you'll have to cut one yourself. Place the fog lights on your bumper and trace them, then cut a hole to fit. If the hole is slightly larger than the lights themselves, don't worry. Your fog light kit should come with an outer plastic piece that will seal the hole.
Mounting fog lights
Some drivers prefer to mount their fog lights on the exterior of the vehicle, rather than installing them in the bumper. This can be easier on trucks or SUVs, especially if the bumper doesn't have a place for fog lights. When purchasing a fog light kit, look for one that's meant to be mounted. The wiring will be the same as wiring fog lights for your bumper.
Instead of fitting the lights into the bumper, you'll find a place on the vehicle to mount them. This works best when your vehicle already has a grill or rack for fog lights. Your fog light kit should come with the hardware needed to attach the lights onto any metal part of your vehicle.
Most trucks or SUVs will have holes already in the grill or rack where the fog lights can be attached. If not, you may need to drill holes yourself to attach the new fog lights.