Brake lights don't work when headlights are on

The title about sums it up, brake lights don't seem to work whenever the headlights are turned on. also, the taillights don't appear to work.

recently bought a 91 4runner 3.0 v6 5-speed manual with 178k miles in pretty good condition but seems to have some electrical problems. a previous owner had installed an aftermarket radio, speakers and subwoofers. they did some funky stuff with the radio wiring and ripped out the woofer and stereos before selling leaving the wires. I paid someone to help me look at it and he said he thought it was the headlight switch, changing it out did nothing for the problem.

I'm a beginner when it comes to electrical, but if anyone has any clues where i might start, I would like to try to look at it myself before having to pay for more diagnoses that may or may not lead to a solution

Thanks for taking the time to read and reply.

 

I had the same issue when I had an 86 Monte Carlo. Would d up being the dimmer wire was grounded to the body and was causing turn signals and brake lights to not work. Not sure if that helps but just throwing it out there.