A new wiring harness would probably be a plus. Ditto on rustednuts advise of checking all of your terminals & grounds. You can use a multi-meter to check your brakelight sending unit. If you get power in but not out the sending unit is bad.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.