The headlight dimmer switch is the electrical switch that is used to control the vehicle’s headlight functions. For some vehicles it is a lever that is mounted on the steering column, while on others it may be a button or knob mounted on the dashboard or center console. The dimmer switch is primarily used to switch between the high and low beam headlights, however in many vehicles it also controls the vehicle’s interior lights as well.
As the dimmer switch is used quite frequently, every time the vehicle’s lights are turned on, it can be susceptible to wear over time and eventually need to be replaced. Usually a bad or failing headlight dimmer switch will produce a few symptoms that can alert the driver of a potential issue.
1. Problems switching between high and low beam
One of the first symptoms of an issue with the headlight dimmer switch is problems switching between high and low beams. If the dimmer switch contacts fail or wear out it may cause issues when switching between or turning on the headlights. A bad switch may not work on certain settings, which will leave the vehicle without that particular set of lights. Depending on which lights are affected, this may problems that may render the vehicle unsafe to drive at night.
2. Headlights stuck on one setting
Another symptom of a faulty headlight dimmer switch is headlights that are stuck on one setting. If you notice that the headlights remain stuck on either high or low beam then that may be a potential sign of a bad dimmer switch. A dimmer switch that is stuck on low will leave the vehicle without high beams, while one stuck on high will leave the vehicle without low beams and blind other drivers on the road if the vehicle is driven at night.
3. Headlights do not function
Another symptom, one of a more serious issue, is headlights that do not function. If the dimmer switch breaks it may not be able to turn the headlights on at all. A vehicle without headlights will have very low visibility both on the road and for the driver, and is not safe to drive, especially at night or in the dark. Headlights can also be disabled by a wide variety of other issues, so having the vehicle properly diagnosed is highly recommended.
The headlamp dimmer switch is one of the most important switches on the vehicle, and can cause a compromise in safety for the vehicle when it goes out. If your vehicle is displaying any of the symptoms above, or you suspect that your headlight dimmer switch may be having an issue, have the vehicle diagnosed by a professional technician, such as one from YourMechanic, to determine if the switch should be replaced.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Headlamp Dimmer Switch and was authored by Eduardo Ruelas.