I have a 1991 Accord. Brake Light is not lighted up

Majdi, if you mean the brake warning light in the dash is on after starting your car, the light is telling you there is a fault/problem with the braking system. You should not continue to drive if the brake warning light is on, as your brakes could fail. You will have to have a good shop check your brakes and diagnose problem and estimate repair. Check the attached links,instruction and guides, Good luck
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Brake lamp warning light Honda Tech
Parking Brake Warning Light
What Causes the Brake Warning Light to Come on
http://honda-tech.com/honda-accord-1990-2002-2/%22brake-lamp%22-light-went-meaning-problem-1723211

Only if the warning light showed on the dash...most often these abs sensors get clogged with brake dust or dislodged during wheel swaps if the pads are fine and fluid level correct...first check the brake pads then the disks and clean the sensors with an old toothbrush and reseat, also check the fluid level on the abs system.this should clear warning light.but any error codes stored on ecu need to be cleared using obd.

Check to make sure your parking brake isn't slightly lifted up otherwise your brake fluid is low

Yes, it could be. Or you can check your battery. And try adding brake fluid to your master cylinder. That sometimes will cause the brake light to come on. Or check your emergency brake. Hope this helps, James Booth.

Has a wireing problem ,best to see an auto electrical shop.

Your brake fluid is low. Fill it up!!!

Brake light switch? Its mounted near the top of the brake pedal lever. The lever contacts and holds the switch closed which keeps the lights from turning on when at rest. When you step on the brake, the contact is broken, the switch extends and completes the circuit allowing the brake lights to illuminate.

CHECK THE FUES BOX UNDER THE DASH BOARD ON THE DRIVERS SIDE.
THOSE LIGHTS ARE COMMONLY ON THE SAME FUSE

You need an alternator.

check to where the trunk latch catches onto, it my be loose and not level.