Headlight Relay
In most newer cars and trucks today the headlight switch actually contains three different switches in one. One switch operates the parking lights while a second operates the driving lights. The third switch is for high beams or bright lights. Most vehicles have headlight switches that use electromechanical devices to control the headlight relays. A headlight relay has a tiny metal tab that is attached by a magnet to the coil of wire that operates the lights. When electrical currents flow through the coil, a magnetic field is created. The magnetic field attracts the magnet that is connected to the relay and pulls the switch to the closed position. If you turn your driving lights on the electrical current flows through the control switch and heads to the headlight relay switch. The relay is closed which then allows a stronger electrical current to flow to the headlights from the car’s battery. Parking lights and high beams or bright lights are also controlled by relays in many vehicles.
In many newer vehicles, light sensors are used in order to control the headlight relay. The sensors can detect daylight, dusk and dark. When daylight is detected, the dimmer parking and driving lights will operate. When dusk or dark is detected, the brighter lights or high beams will operate. As the light gets lower, the sensors automatically detect darkness approaching and signal the relay to begin operating the brighter lights. Most vehicles also have manual operations for headlights as well that gives them the ability to turn on the high beams when they need extra lighting.
When the headlights on a vehicle equipped with a headlight relay are turned on, the power to the coil of the relay closes the electrical current that leads to the headlights. If you own a vehicle with a headlight relay and notice that your headlights are no longer working properly, you may need to have your headlight relay replaced. Fuses can also cause the relay or the headlights to not operate correctly. If you turn on your headlights and only one light comes on then your relay is likely not the culprit. When the headlight relay needs to be replaced, neither of your headlights will work. If only one headlight is working then you may simply need to replace the bulb in your headlight.
To check the headlight relay you can also simply open the hood and listen for the relay to work. With the hood opened, you should hear a click when the headlights are turned on. If you do not hear a click when operating your headlights then the relay may need to be replaced. While many car enthusiasts and repair specialists will encourage you to purchase used parts for many purposes, a headlight relay should be purchased new. You can find these at automotive parts and supply stores and at many online retailers. Headlight relays and switches are very inexpensive and can be replaced very quickly if you have the right tools and are fairly familiar with your vehicle.
If you are unsure of just how to replace the relay, you can find information about replacing headlight relays online or in automotive repair books. You can also simply take your car or truck to your local automotive repair shop and have the relay replaced. Again, headlight relays are typically very inexpensive. Depending on the specific make and model of your vehicle, you should be able to purchase a headlight relay for around $20 to $60. The price you will pay for having the relay installed will depend on the garage that you choose as well as the make and model of your vehicle. Automotive repair shops typically charge by the hour so if your vehicle has a headlight relay that is hard to get to, you may pay a bit more for the replacement.
