When you experience difficulties while driving like a flat tire, running out of gas, or an unfortunate accident, your vehicle can be immobile at the side of the road or worse, in an active lane of traffic. If this happens to you, turn on your hazard lights. The hazard lights on your car indicate to other drivers around you that you are in trouble or are having problems with your vehicle. They tell other motorists to avoid getting too close, and are a signal for help if the hazard lights are combined with an open hood.
How do the hazard lights work?
Your hazard lights are operated by pressing the hazard switch on your dashboard. On some vehicles, there is a button on the top of the steering column shroud, while on older vehicles they may turn on when a hazard switch under the column is pulled down. The hazard switch will activate the hazard lights on your vehicle anytime there is battery power. If your car stalls because you ran out of gas, have mechanical problems, or a flat tire, the hazard lights will work whether your car is running, the key is in the ignition or not.
The only time the hazard lights will not operate is if the battery is completely dead.
The hazard switch is a low-current on/off switch. When activated, it completes a circuit. When it is deactivated, the circuit is opened and power no longer flows.
If you’ve pressed the hazard switch:
Power is routed through the hazard light relay to the signal light circuit. Hazard lights use the same wiring and lights as the signal lights. The low-current hazard switch enables the relay to send current through the lighting circuit to the flasher.
The flasher relay pulses the lights. When power runs through the signal light circuit it goes through a module or flasher that only emits a pulse of power rhythmically. The flasher is the part that makes the lights flash on and off.
The signal lights flash continuously until turned off. The hazard lights will continue to flash until the hazard switch is turned off or there is no longer power flowing, meaning the battery dies.
If your hazard lights don’t function when the button is pressed or they turn on but don’t flash when engaged, have a professional mechanic inspect and repair your hazard warning system immediately. It is a safety system and must operate at all times.
This article originally appeared on YourMechanic.com as How Does the Hazard Switch Work? and was authored by Jason Unrau.