Any mechanics and/or electricians in the house?

[Kara]

So my car is doing something REALLY weird. I don't know much beyond putting gas in the tank. My fiancee can do a lot of work (and she has done some work on my car), but for this she says she'd need to know what the problem is and how to get to it. 2 weeks ago, I got in my car after work and my foot hit the brake pedal when I was getting in. The parking lights and the dash board lit up. I pressed the pedal again, parking lights and dash lights come on. Oookay, that's different. Then I noticed on my way home that my brake light in my back window was on. I wasn't using the brake, my emergency brake wasn't on, but the brake light stayed on all the way home. I found that whenever I turned my headlights on, the brake lights also came on (all of them). It had NEVER done this before. Then after a few days, it stopped doing this. Then a few days later, it started up again. Tonight, lights were behaving.

It's clearly something electrical, but we haven't messed with any of the wiring. Fiancee did have to replace the main fuse back in October, but this didn't start happening until 2 weeks ago, so I don't think it could be that. She said her best guess without looking at it (we just haven't had the time or someone's been sick when there was time) is a wire got crossed, but we have no clue how that could have happened.

The only history of funky lighting issues my car's had is that my dome light is very finicky and has been for 4 or 5 years. Sometimes it works and sometimes it doesn't, but I haven't ever given it much thought and I don't know if it's related.

[Gravekeeper]

I know fark and all about mechanics, but that sounds like an electrical short. Provided this isn't a newer car with computer controlled lights. You didn't mention the make and year of the car so don't know if its something specific to that car.

That said, if someone's recently looked at the wiring, check the lights and sockets themselves. If there's a bad ground somewhere in the light/socket it can cause that. You may just have one light that's got a bad ground in a socket. If its coming and going then it might be being jarred by the vibration of the vehicle.

So check your bulbs and sockets, see if they need to be cleaned up or if anything has shorted or melted around the socket. if you're lucky you've just got one bad break light that's causing it all and its an easy fix.

[Kara]

It's a 98 Mazda 626.

I mean, it COULD be my latent psychic/magic powers awakening. Streetlights tend to go out when I get near them >.>

[Gravekeeper]

It's a 98 Mazda 626.

I mean, it COULD be my latent psychic/magic powers awakening. Streetlights tend to go out when I get near them >.>

Street lights seem to do that for practically everyone either because the light is old and has begun cycling ( turns on and off periodically as it heats up and cools down ) or something has tripped its daylight sensor. The daylight sensors on street lights are typically pointed in the direction of first light instead of up. So they can be tripped temporarily by a passing light source or light scatter from that direction. The rest is observational bias. >.>

- Scientific Debbie Downer

So yeah, check your break light sockets and bulbs if no computer is involved. =p

[Chromatix]

So, it's a 15+ year old car.

I would strongly suspect decayed wiring insulation. That will cause intermittent shorts from wire to wire, which could cause the symptoms you describe very easily. You don't mention any fuses blowing, but that's consistent since the ground return path in most cars is via the chassis.

In many cars, a lot of the wiring (that isn't part of the engine itself) is in a large bundle of wires called the "wiring loom". It's best to replace that all in one go. It's also a pretty substantial job, best done in spare time if the car isn't worth much - some of the wires will lead to the rear of the car via channels in the chassis, which you'll need to remove interior trim to access.

[wolfie]

When the brake light was on all the way home, did you have the headlights (or at least the parking lights, or does your car have daytime running lights) on? Sounds like you're getting an intermittent short between the wire for the brake lights and the wire for the parking lights.

Reasoning: dash lights and parking lights are usually on the same circuit. If that's shorted to the brake light wire, hitting the brake pedal will light them up along with the brake lights. Similarly, if the parking lights are on, the short will cause the brake lights to come on too. The fact that it happens sometimes but not others means it's an intermittent.

Is there any pattern to when it happens and when it doesn't? If it happens more in wet weather, the "sneak path" could be through corrosion (conducts better when wet). If you're dealing with corrosion, the entire length of the affected wire(s) will need to be replaced - one pinhole letting water and road salt in can result in "wicking" that leads to FEET of the wire corroding - a common problem on truck/trailer electrical systems.

[Kara]

- Scientific Debbie Downer

:P :P :P :P :P :P :P :P :P

When the brake light was on all the way home, did you have the headlights (or at least the parking lights, or does your car have daytime running lights) on?

Yeah, it's dark when I get off work and it happens when my headlights are on. I haven't really noticed any pattern at all. It's been cold and and a little wet, but nothing too bad. And that doesn't seem to affect anything. So far it just seems purely random

[protege]

So check your bulbs and sockets, see if they need to be cleaned up or if anything has shorted or melted around the socket. if you're lucky you've just got one bad break light that's causing it all and its an easy fix.

It sounds like something has burnt, and is now shorting out. Fried wiring can lead to some strange results. I know one guy, who had some welding done on his car...and the shop in question didn't bother to protect the wiring. Pressing the horn, would spin the starter

What I'd start with, is this forum which has lots of info about your car. Someone over there might have dealt with the same problem. BTW, I do know that Mazdas of that era (I had an '00 Protege) would develop some odd electrical issues--gauge clusters that sometimes wouldn't work, door locks not opening from inside the car, etc.

[Gravekeeper]

It sounds like something has burnt, and is now shorting out. Fried wiring can lead to some strange results. I know one guy, who had some welding done on his car...and the shop in question didn't bother to protect the wiring. Pressing the horn, would spin the starter

A short anywhere can do some really weird things. But ruling out the break lights and sockets first is easier than crawling through the wiring first I would think. Unless this make of car has some unique electrical problems.

When was the last time the break lights were replaced? If ever. >.>

[It's me]

As already noted, clearly an electrical short. Assuming no mods have been made to the car, I suspect this is on occurring at one of the tail lamps. Either internally in the bulb, or there is a fried socket, maybe wires rubbed through where there is slack to allow the bulbs to be removed. If the car has an add on remote starter (not FACTORY installed, but by dealer or third party) I'd also suspect those connections.

Edit:
And yes, if I had been paying attention I would have seen others already specifically mentioned it might be a bad socket.

[mathnerd]

I don't agree that it's "clearly" an electrical short, though that's the most likely problem. A car that old could have a mechanical brake light switch that's getting stuck in the "on" position from intermittently, which could cause the symptoms described. That's an unlikely scenario, but still possible and worth checking out. Replacing a brake light switch is super easy, so it's worth a look-see.

[sms001]

Street lights seem to do that for practically everyone either because the light is old... or something has tripped it....

Or you're Thor, trying to get Kate Schechter's attention.

ETA:

Or, apparently, if you are driving a KIA with Laurence Fishburne singing opera in the backseat.