Lights (Headlight / Brake lights) not working

The headlights and brake lights on a vehicle are absolutely essential for safe driving and in many cases it is illegal to drive if they are not functioning correctly. Problems with the light system can range from a simple blown bulb to something more complicated like a faulty socket.

Regardless of the reason, lights that are not functioning can lead to dangerous driving conditions, so the lighting system should be inspected and repaired as soon as possible.

How this system works:


There are a number of different types of headlight systems but they all do the same thing: light up the road in front of the vehicle.

In a common halogen system, the headlight housing is where the headlight bulb sits. The inside of the housing is covered with chrome paint that reflects the light down the road. The chrome piece that coves the actual bulb is there to prevent the bulb from blinding oncoming drivers. They are powered by the vehicles electrical system. They can be toggled between a high and low beam. These systems use a halogen bulb.

Brake Lights

Brake lights illuminate when the contacts in the stop light switched are closed. When a driver steps on the brake pedal, this closes the switch, which sends power to the bulbs, which lights up the bulbs.

Common reasons for this to happen:

Brake Lights

  • Blown Fuse: The electrical power for the brake light system passes through a fuse and if the fuse blows, the brake lights will no longer work. While this is usually a simple fix, it could indicate a larger problem. If the same fuses continue to blow, the brake light system should be inspected.
  • Burned Out Bulb: Like any light bulb, vehicle bulbs will burn out over time. At some point in the lifespan of a vehicle the brake light bulbs will have to be replaced. Time frames differ depending on the bulb type.
  • Malfunctioning Brake Light Switch: The brake light switch works like a household light switch. When the brake pedal is depressed it closes the switch to send electricity to the brake lights. If the switch is faulty it breaks the connection between the brake lights and the pedal. The brake lights will no longer work, or they can become stuck in the on or off position.
  • Issue with Bulb Socket: The sockets that the brake light bulbs sit in can be dirty. If the debris builds up on the contacts in the socket it will prevent the bulb from making contact and consequently, will not light up. In this situation, you’ll notice that only one of the brake lights will not work, as it is uncommon for both sockets to become blocked at the same time.

Unplugged Harness: The electrical system that runs the brake light system contains various harness and if one of them becomes unplugged or defective it will affect the brake lights.


  • Fused Bulb: Just like the brake lights and every other bulb, eventually the headlights will burn out and need to be replaced. Bulb life varies depending on what type of bulb the vehicle uses. In most cases, if only one headlight is not working, replacing the bulb should be the first step.
  • Blown Fuse: Just like the brake lights, the electrical system that runs the headlights incorporates fuses and if one of them is blown the headlights will not work. If you cannot switch between high and low beams, a fuse could very well be the problem.
  • Faulty Relay: If both headlights are not working, the headlight relay is one of the most common causes. The headlight relay is part of the electrical system and if it is malfunctioning, the lights will not get power. The relay will have to be replaced.
  • Faulty Headlight Switch: The headlight switch is used to turn on the lights. If the switch is malfunctioning the headlights will not function. If it is impossible to turn the headlights on the car should not be driven at night and should be repaired immediately.
  • Faulty Socket: The socket that the headlight bulb sits in can become dirty or contaminated. If this happens the bulb cannot make the contact it needs to light. In this case, the most common symptom would be one headlight not working.
  • Moisture in the Headlight Housing: If the headlights turn on but are not illuminating the road there could be moisture in the housing. This will cause fogging and diminished performance of the headlights.
  • Faulty Dimmer Switch: The dimmer switch allows the driver to switch between high and low beams. If the switch is malfunctioning the headlights can become stuck on high or low.

How important is this service?

The lights are a major safety component of the vehicle and they should be maintained to ensure safe driving conditions. Malfunctioning lights should be inspected and repaired as soon as possible.