Brake Light issues...PLZ help!!

my brake lights seem to be growing a mind of their own over the last couple of days. when i push the brake pedal with no key in the ignition, my brake lights appear to work fine, but the ac/heater control panel lights up as well, but the fan does not turn on. with the truck running , the brake lights are fine, and the ac/heater controls turn on as well, and the fan does run. now the problem; when i turn on the lights,everything appears alright, then when i press the brake pedal, one brake light turns off, the same side reverse light turns on; when the brake pedal is released, the running lights return to normal.
i have checked the fuses (DMM), replaced the brake light switch, checked the bulbs (DMM), and banged my head and skinned my knuckles..... anyone else have any sagely advice as to what the problem might be??

any insight would be greatly appreciated.

check the grounds or the bulbs and head light switch

turns out there was a bad ground in the heater/ac controls..... don't know why there would be a connection between that and the brake lights..... but she's working now.