1993 ford mustang brake pedal goes down on its own and brakes

Did you overheat this engine?

You have a short in the brake system wires. Id start disconnecting everything one at a time until the dimming goes away. Then that component will be your issue. Whether it has failed or the wires going to it are shorted will depend on diagnostics and what it shows.

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Did you change the bulbs? It might also be bad wiring. You can check the wiring by using voltmeter connected to the brake light and then have someone depress the brake pedal. If there is not 12- 14 volts on the meter then you most likely have a loose or broken wire somewhere.

check fuses for brake shift solenoid. the brake pedal position switch is a fuse under the hood. inside the passenger compartment, check every fuse. that's a start for not having more information.

break lug nuts loose
jack up car place stand under car
remove lug nuts and wheel
remove brake caliper
take out pad on outside of caliper
place a brake caliper press on pad next to piston of caliper and compress piston back in caliper
remove press and replace pads
reinstall caliper and wheels set car down
REMBER TO GET IN AND PUMP BRAKE PEDAL A COUPLE TIMES OR YOU WILL NOT HAVE ANY BRAKES WHEN YOU MOVE YOUR CAR!!!!!!
check fluid in master cylinder
take your time

probably the brake pedal switch (mounted on the brake pedal lever) starting to fail. it releases the shift lever and controls the brake lights coming on. you will need to replace this.

for now, turn the key in the ignition to the lock position (counter clockwise,) then to the off position (clock wise). In this position the brake shift interlock is disabled and you can move the shifter to neutral. these instructions are also in the owners manual in the driving section.

Sounds like the front calipers are not fully retracting properly. Check the front caliper operation while a friend pumps the brake pedal, the rubber lines could also be cracked and allowing air into the lines. Check brake fluid level.

Have the brakes purged, bled, adjusted & bled again.

It is on the steering column, but those rarely go bad. dont forget to accept the solution.

make sure brake fluid is full. then pump brakes for one minuite check the fluid to see if it went down or stayed full. if it went down then check the system for a leak . if it stays full then you will need a new mastercylender . i dont think you have a vacum problem cause this causes a verry stiff brake pedal not one that goes to the floor