Break light

I have a 2002 Ford Explorer. The break lights won't turn off. What could I check?

If it is the lights on the rear of vehicle, look at the brake light switch mounted on the brake pedal. It should be mounted on the part that comes down from under the dash.

How can I check if it's the switch. Should I just buy a new one?

You can unplug the connector and lights should go out. If lights go out, then replace the switch. If lights do not go out, look for a wiring problem.