ok so last night my speedo cable crack and when that happened my light went out and wouldnt come on. and my car wouldnt start(weird). so later that night everything started working again. today my friend was flicking my headlight on and off and then. my headlight stopped working again. this time everything fucked up. this is a 89 hatch im talking about with ls swap. ok so. know whenever i press the brake my check engine light,oil light etc. come on. wtf! my car also wont start and stay on.my friend says i might have fried one of the gounds on the dash harness.my gauge cluster shows the car as past hot on the thermostat.also my car is throwing code 6,10,13. man this is so weird. i dont wanna sell my car but i have no clue what could be wrong my main relay will start ticking sometimes. if anyone know what i should be looking for to try and fix this le me know thanks

 

Sounds like a loose or corroded ground. See what all those circuits have in common and start troubleshooting.