BRZ TAIL FUSE BLOWING
 

I recently bought a brz from Craigslist and totally forgot to check the lights before buying the car (because it was daytime). Rookie mistake on my part, however, I bring the car home to realize the tail light running lights and the license plate lights don’t work. When I took the bulbs out of the plate lights, they were cracked so I tried replacing them, putting a new fuse in, and hoping it would work. It didn’t. The fuse pops under the dash whenever I turn the lights on. The break lights and blinkers work perfectly, however, may it be a possibility the DRLs don’t work because I don’t have front headlights in? If that’s not an issue I believe it may be a grounding issue or a short somewhere in the tail light wiring or the plate light wiring, but before I go digging through the car, is there anything else I could try or may have forgotten to do? Any help is greatly appreciated.

Headlights are on a different fuse. If you blow the fuse as soon as you turn the lights on there is a dead short someplace. Good luck!

Meaning that the headlights have no effect on the tail light short? So then when I search for a short, would it be visible (exposed wires, cut grounds, etc.) or could it be a pin connector issue as well?

Anything is possible.

I would start by disconnecting the trunk lid connector under the rear deck. If the fuse doesn't blow, that eliminates the vehicle-side harness, and narrows down the issue to the much smaller trunk lid harness.

Or it eliminates the trunk lid, and the rest of the harness becomes suspect...

Yeah I disconnected literally everything in the trunk one by one and the fuse kept blowing. Tried using a 15a as well and it still blew. It’s weird because my side marker lights work which is on the same circuit too I believe. If i tried everything in the trunk area, could it be something in the dash? At one point a subwoofer was in the car and I think this may be a culprit.

*EDIT*
Would anyone be able to tell me what other lights besides the tail lights and plate lights are using the “tail fuse”. Could the trunk lights, headlights, interior lights, door lights, be part of the circuit?. I’m not exactly sure, so any help is appreciated.

Bear in mind that if you have a wiring issue where it's shorting somewhere in the harness itself, disconnecting things isn't going to show the problem. So with that in mind, if you have disconnected all the lights and it's still blowing the fuse, your problem could be in the harness itself.

Also, if the fuse has blown but the side markers are still turning on, then the side markers aren't on that circuit.

there's harnesses that run down the length of the car next to the door sills on both sides.

the next step, i would go full-in, and pull the interior on the car, inspecting the harnesses for damage along the length going towards the back. it's easier to pull the trunk panels than remove all the seats, so i'd start in the trunk inspecting any wiring harnesses for damage there.

and don't install a larger fuse. if it's blowing immediately, it means there's a short. even assuming that a larger fuse did hold, it would only raise the risk of fire/damage later, making the problem larger than it already is.

Going to take the side panels/skirt panel off and see if I find anything. I’ll update you guys in little to see if i find anything. Thanks.

I you can wire a 12v light globe across the two fuse terminals it will illuminate brightly whilst the short is present. If you mess with the wiring and stumble across the short circuit you will see the light dim or go out. Then you know where to inspect more closely.

Here is the location of the connectors carrying the wiring from fuse panel to trunk. As @soundman98 advised, you could disconnect JH2 and see what effect that has on the fuse. Be careful with HD1. There are many circuits other than rear lights in that connector.

Thank you to all who helped. I tried using a 12v light, I took apart pretty much the entire interior, trunk, and traced all wires down the car. Maybe I’m just exhausted and missed it, but no short was found. At this point I’m going to just drop it off tomorrow at an auto electrical shop. Bummer, but at least I tried and will give the electrician a head start. Again, Thank you to all of those who pitched in ideas, you were all super helpful.

Side marker lights for the FR-S are connected to the license plate lights, but I'm not sure if that's the same for the BRZ. Years ago I had a fuse blow on that circuit due to a loose license plate bulb that had a slightly smaller than normal base. If the fuse is blowing every time then sounds like you might need resistors or that circuit is being overloaded w/ whatever bulbs were installed - did you try replacing the bulbs with stock ones just in case the previous owner installed ones with way too high power/draw? Hope whatever your issue is ends up being minor/fixable and good luck.

Hey I know this thread is crazy old, but does anyone know what the solution ended up being for this guy? I’m having the same issue myself on my Scion FR-S