Troubleshooting Headlight Problems - Tips and Tricks | HEART Certified Auto Care (2024)

FAQs

How to troubleshoot headlight problems? ›

Headlight Fuse or Relay

If a headlight fuse blows, it could cause the headlights to stop working. Most headlight systems are also designed with a relay that switches the power between low beam and high beam headlights. If this relay goes bad, it could allow power to the high beams, but not the low beams.

To narrow down where the fault has occurred, you can examine for the stoppage in current flow to determine whether it's closer to the sensor or load. If you reconnect a wire and fuse for the headlights and the test light goes out, you can narrow down the issue to the area between the switch and the load.

Most total headlight failures are caused by a bad component like a fuse, relay, or module. Wiring problems can also cause both headlights to stop working. High beam headlights don't work or low beams don't work. The cause: A burned out bulb, or a problem with the high beam switch or relay.

Find the adjusting screw and turn the screws slowly clockwise to raise the height of the lights or counterclockwise to lower them. As you make your adjustment, make sure the most intense part of the headlight beam hits at or just below the vertical centerline you taped on the wall. Adjust the horizontal field.

The headlight relay is typically located in the power distribution box in the engine compartment. Consult your owner's manual if you need help finding the relay. How Much to Replace a Headlight Relay? Replacing a headlight relay is a DIY-friendly repair that you can usually do yourself.

Do all cars have one fuse for their headlights? No they usually have 4 fuses. Left high beam, left low beam, right high beam; right low beam. Hope this helps.

Burned-Out Headlight Bulbs

If both of your low-beam headlights are out, but both of the high-beams work fine, it's possible that both of your low-beam halogen headlight bulbs have simply burned out.

Your car's headlights work together to illuminate the maximum amount of space in front of it. If one of the headlights stop working, it will leave a significant swathe of road in the dark. Second, driving with one headlight makes it harder for other drivers to notice your car.

Does each headlight have its own relay? ›

One of the common causes we frequently encounter for the malfunction of low beam headlights, while high beams continue to function, is a faulty headlight relay. In essence, relays serve as electrical switches, and both the low and high beams have their dedicated relays.

Connect the black (negative lead) of the multimeter to a good ground on the frame or to the negative battery terminal. Set the multimeter on the voltage scale for 20 volts. Turn on the headlights and select low beam with the dimmer switch. The reading should be around 12.4 volts or so.

However, the issue causing the failure is usually going to be more complex than bad bulbs if both lights go out simultaneously. In this case, you may need to go through and test out the headlight fuses, switches, and relays. The easiest of these components to check is the fuse.

How to check if your headlights and taillights are working. The easiest way to check if your lights are working is to turn the engine on and leave the handbrake on. Then turn on each light and walk around the car to visually check them.

The relay circuit board is located in the engine fuse box. It's the long black module in the lower right of the fuse box. It contains several relays not just the headlights. As for jumpering between the driver side and passenger side headlights...

The good news is that headlight systems are simple when compared to other systems in your car. Most headlight systems are going to involve a fuse, switch, relay, and bulb.