Wankels-Revenge

Ok see this was originally intended as a pm for icemark, but seeing as how i can no longer pm anybody i might as well make a thread about it.

So ya...the brake lights dont work when i press the brakes. It can either be the switch or the CPU. I changed the CPU already from one i bought from icemark's site, so that can't be the issue. Its most likely the switch. But that wasn't my question anyway *insert smiley face here* (i dunno how to navigate this upgrade yet..).

Anyway, the previous owner did some seriously screwed up wiring job and for some reason decided to wire up the brake light switch to the CPU himself instead of using the plug on the wiring harness *insert confused face here*....

My question is, the two wires going to the brake light swich connectors should be a green wire with a white stripe, and a white wire with a green stripe right? If thats the case i also have another plug with a black wire with a yellow stripe, and a solid yellow wire....where the hell does that thing go?

Any help from anybody would be appreciated! But icemark, this is your territory so I hope you see this.

Icemark

The circuit (on a S4 and much simplified) works like this.

Ignition to switch, switch to CPU, CPU to lights.

Does the switch have 12volts when the key is on??

Does it switch to the other wire when the brake is pressed?

Wankels-Revenge

I'll run out and check that right now. Just out of curiosity, do both wires coming off of the switch go to the CPU, or is one a ground or something?

Wankels-Revenge

Now i dont even know if i did it properly, but one wire only has like 0.25 volts with the ignition on, but it does switch to the other wire when the brake pedal is depressed.

Also, how loud is that "click" supposed to be when the switch is released after the brake pedal is pressed down, because on mine it sounds pretty faint and..well...broken haha.

Im still trying to figure out what the hell the previous owner did. When i first got the car the stop lights didn't work, so thats the first thing i tried to fix. When i looked at the switch at the brake pedal for the first time, there were two wires (separate, not in a plug). One wire was plugged into one of the connectors on the switch and led to the CPU. The other wire was connected to the other connector, and was hooked up to the negative terminal of the battery.

I jiggled the wires a bit the first time and that seemed to fix it. When the stop lights WERE working, the little stop light warning light would always come on whenever i pressed the brake pedal....thats how i knew when the stop lights worked. Sometime during the winter the stop lights crapped out again and now im back to where i started, only this time i found the original plug that was meant for the switch, and now i'm trying to figure out what the hell they were thinking.

Any ideas?

Icemark

Okay, lemme look at the manual,

There shoud be at the switch a Green/White that has 12 volts on it all the time. This is the same lead as the Horn relay uses, so you can check to see if the circuit has voltage by if the horn works.

Then there is a white/green at the other side of the switch. If you have a S4, then this wire goes directly to the CPU's bottom 4 pin plug. This wire should have 12 volts on it when you press the brake pedal, and might have a half volt to nothing any other time.

When you apply 12 volts to that white/green wire (Jump it from a 12 volt source) the brake lights should come on, and the solid green wire in the 4 pin plug at the CPU should also have 12 volts on it. The solid green is the wire running to the brake lights themselves.

If the CPU is not working, as a test you could just jumper the white/green to the solid green at that 4 pin plug at the CPU and the brakes lights should also come on if the switch was working ok

Wankels-Revenge

Hrmm that might just be it. My horn doesn't work either...or it only works occasionally. The thing is i just changed my CPU so the circuit SHOULD be working. I'll definately look into checking the CPU out and making sure that the wires are ok. Thanks again for the responses icemark. You're a lifesaver!

-James

Icemark

Check your Horn fuse

Wankels-Revenge

I did...it seems ok but i'm gonna replace it anyway.

I also checked the connector inside the steering wheel to see if it had 12V on it with the car on...but nothing. Same with the brake switch. I'm gonna keep checking for other possible causes, but something tells me its the wiring.