Q: How Does the Hazard Switch Operate?

The hazard switch, (also known as the "emergency flashers",) is a vital part of your vehicle’s safety system. The switch is typically located within easy access to the driver and has a red triangle located on the switch. The main use for the hazard switch is to turn on your four way flashers to either warn other drivers that your vehicle is in the way of traffic due to an emergency stop, or to notify them that you are having car problems. Once the switch is pressed, it will flash the exterior marker lights until it is pressed again. The function of the hazard switch and how it works depends on the vehicle’s design.

The hazard switch itself is essentially an on-or-off switch that locks itself in the On or Off position once it is pressed, and the hazard circuit is closed. Once there is power to the circuit, that power is directed to the hazard flasher; the power either comes from the fuse box, or from the switch itself. Once the switch is on, the voltage going through the flasher heats it up and eventually breaks the circuit, turning the switch off until it cools. Once it cools, the circuit closes again, turning the switch back on. This occurs in a rhythmic on-and-off way, which explains why your hazard lights flash on and off, over and over again, in what appears to be perfect timing. On some modern vehicles, the switch does nothing more than send a signal to the computer that you have turned the hazards on. The computer then controls the on and off of the hazard lights itself.

If you have any problems with the hazards not working, it is commonly due to a bad flasher. It may also be a switch problem, which is not as common. In either case, the hazard light issue should be diagnosed by a certified mechanic, such as one from YourMechanic, and replaced if necessary.