Break light fuse keeps blowing


Hi. Like the description says my break light fuse keeps blowing. I replaced the break light switch switch and checked the break lights by installing one at a time then breaking. Both time the fuses blew.

I didn’t notice it until a guy driving behind me let me know yesterday. I think this may have to do with a sub install a few months ago. When I was passing the positive cable for the sub through the firewall I must have done something because my esc warning light came on and I lost the ability to set cruise control. I did notice when I replaced the break light fuse today, before replacing the break light switch, My cruise control came on.

Could this issue have to do with the wiring in the radios wiring harnesses?

I’m pretty sure there’s a short. I’m wondering if its at the grommet in the firewall where I passed the positive cable for the sub.

Any advice on how to get the grommet out and how to inspect the wires would be appreciated.

Thanks in advance.

If it has a lift tailgate I would look there for a short or broken wire, but that’s me

Does a Break light tell you something has broken ?

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you know what the OP means. Is it really helpful to bust everyone’s chops all the time? if so: why the space before your question mark? Does that do anything to emphasize your question? Typos and words spelled wrong happens. Learn to live with it, or find a different hobby.

@jameson.luttrell_154832 - since the issue with your brake lights happened immediately after you installed your sub, this is a good place to start. Recheck your work, and follow all the wires you added- looking for breaks, scuffs, rubs. Since we cannot know how you tied into anything to power your sub, we really can’t point you in a definitive direction. We also have no idea of your ability, knowledge, or expertise, so no idea what you could have done. Start with double checking your work. Unhook the sub, radio, etc. in sequence and see if any of that helps.

Also, as @Barkydog suggested: check the wiring in your liftgate. This could be unrelated to your work.

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Thank you.

Does anyone know what color the Brake light switch is?

looks like black and/or grey.

Thank you. Do you know if they go strait to the fuse box?

I’m going to point you here:

Some folks post wiring schematics on here for various things, but it looks like they may be able to help with more specific Kia info more than I can.

Others here may be able to help, but I have literally never touched a Kia- so you are out of my realm. Good luck!

in fact, here is a Kia Rio brake light search:

Thanks. I’ll look at it now.

I found there’s a short after the brake light switch. I have a feeling its right at the grommet going through the firewall. I have no idea how to get access the wires to inspect them. I just got laid off right after taking over a lease so taking it to a mechanic is not an option.

Can I just cut the old wire where the short must be at and solder a new wire and run it back to the lights?

I’m having trouble understanding this. Is there a relay between the lamp switch and the brake lights? Where could I find that?

didn’t you say you ran a wire for your sub though this grommet? If so, then you know where to start.
If the grommet is just rubber, it will pull out- just be careful. It may be a bit of a pain to put back in.
If the wires are in a plastic sleeve, you can pull the plastic back and see inside.
there should be some play in the wires, nothing should be so tight it won’t move at all, but the grommet or whatever is being used to pass wires though the firewall should be water tight- so it will be snug.
The grommet should also be thick enough to keep the wires away form the metal edges. Perhaps a visual inspection both under the hood and under the dash will show if something has moved close to a metal surface?
it sounds like you have a short to ground (thus the blown fuse,) so look for exposed wire or wire rubbing metal.

as for your stop light relay: if that schematic is for your vehicle, then it does look like there is a relay. it should be in the underhood power distribution box. the lid of this box may be labeled with what each relay is. if they are similar, you can try swapping it for a different one to test- like the wiper relay.

it’s your car, you can do whatever you’d like. But based on the schematic, it looks like other things are running off of those wires. Depending on where you cut and splice in, other things may not work.

I just took out a high to low converter that I was using to run a sub from my stock radio and the lights work again. I didn’t think any of the wires have anything to do with the brake light circuit, but apparently they did. Thanks for your help.

I’ve had that sub in for about five months. I’m pretty surprised I never got pulled over.

That section of the circuit diagram doesn’t show the tail-lights. The reason the ESC is involved w/the brake light circuit is b/c to do it’s “stability” job the ESC needs to know when the brakes are being applied. The middle/lower block refers to a “stop lamp relay”, so I assume there is one. It may not be the normal relay in a little box though. You need the rest of the circuit to figure this out probably. See on the lower right it says “See Stop Lamps” followed by a reference number? Try to find that section too.

Since this problem appeared immediately after you installed some entertainment system electronics, almost certainly is caused by something you inadvertently did. Usually just following the affected wires eventually turns it up, wire insulation rubbed off, bare wire touching chassis, etc.

If all else fails there’s a wiring debugging gadget available that would make finding the problem easier. You connect it to the circuit, then it sends out an electronic pulse, and you pass a wand over the wire. The wand detects the pulse, makes a sound. At some point you won’t hear the pulse any more. That’s where the circuit break or short is located.

Note: Good idea to first disconnect battery before working on the electrical system.

Thanks. I figured it out. I am going to look into getting one of those gadgets for tracking down shorts.

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