Without looking up the electrical schematics, it sounds like your brake lights are have a bad ground. With the headlights off, the brake lights are using the headlights as ground. When the headlights are turned on, This prior ground path is now hot. So, the brake lights do not work. This is just a guess. So, hypothetically, cleaning the grounds would fix this. A possible test would be to provide a ground path for the brake lights.

Remember, only a guess
Good luck

 

Awesome info, thanks man! When you say to clean the grounds, how would I go about that? Pretty new to DIY, just want to make sure I understand. Thanks.

 

He meant clean the CONNECTIONS to the ground wires. This simply entails unscrewing the bolts that hold the wires to the body a few turns, then tightening them again. That usually fixes things (unless there is collision damage in the car's history, we had that on one of our used cars, once).

I'm sure that if you SEARCH you can find locations of ground bolts, in the back. A volt-ohm meter would help verify if you have good connections, too.

Don't be scared of electricity...

 

He meant clean the CONNECTIONS to the ground wires. This simply entails unscrewing the bolts that hold the wires to the body a few turns, then tightening them again. That usually fixes things (unless there is collision damage in the car's history, we had that on one of our used cars, once).

I'm sure that if you SEARCH you can find locations of ground bolts, in the back. A volt-ohm meter would help verify if you have good connections, too.

Don't be scared of electricity...

That’s what I kinda figured, I did some digging online and it looks like the ground I’m looking for is G601. There’s no diagram or information showing where it is, but according to this site, it’s behind the right quarter panel. I’ll just need to find the ground wire and trace it back to where it’s bolted to the frame right? Clean the connection and make sure it’s tight and then theoretically I’m good to go?

Also I’m definitely scared of electricity haha. Did you mean that like I shouldn’t worry about getting overwhelmed with it or was it a sarcastic way of saying to be careful?

 

Are you sure they are the right bulbs also? The brake lights should be twin element. One For lights, the other for the brake circuit.

 

I’m sure it’s a possibility, but I’m not sure that the bulb type would be to blame since the brake lights do work when the headlights aren’t on. I’m planning on getting a new set of headlights and brake lights regardless of what the issue is, so we’ll see.

 

Alright y’all, small update. I changed out the bulbs. Passenger brake light is at 100% functionality but the driver’s side brake light has only one working filament (the ones I bought have 2). This causes the light to work as a running light when the headlights are on, but when applying brakes, the entire light turns off. I’m thinking it might be a bad connector, but it’s hard to say. I also replaced the 3rd brake light and it hasn’t started working either, so I’m going to try and new connector on that one and see where it gets me because it does look kind of ratty.

Mine is a European sourced model according to the VIN.

What should my next step be other than trying to locate the ground and see if it needs cleaning/adjusting?

Cheers!