It may be because you are braking.
If you mean the " BRAKE " light in your dash it's just under the " 0 " on your tachometer
If the red " BRAKE " light comes on in your dash , either the parking / emergency brake is on or the BRAKE FLUID LEVEL in the brake master cylinder ( in the engine compartment of a Ford Explorer ) is LOW
Look at the upper end of the brake pedal under the dash area
If the brake light in your dash is on , either the BRAKE FLUID LEVEL in the brake master cylinder in your engine compartment is LOW or your parking brake is on
The brake warning light comes on in your dash if the emergency brake is on or the brake fluid level in the brake master cylinder in your engine compartment is LOW
check the brake light switch it might be sticking. located under the dash connected to the brake pedal
If you are speaking of the brake light on the dash, you may be low on brake fluid. Just fill the master cylinder with DOT 3 brake fluid, and the light should not come on anymore.
Where is brake light fuse for 2004 Ford Explorer located
It could be a fuse , a sensor , or some other problem with the antilock brake system ( as long as the red " brake " light in your dash is not on you still have " normal " braking )
To replace the brake light on a 2000 Ford Explorer, remove the screws holding the brake light in place. Gently, but firmly, pull the brake light out of the vehicle and replace with a new one.
Sounds like it could be a problem with your brake light switch mounted on the arm of your brake pedal under the dash.
bulb # for brake light on your explorer is a 3157 backup light bulb # is 3156 hope this helps