Fog Lamp Relays

[mph]

What the hell do relays do? I unplugged the relays for the fog lamps, low beams, and high beams and they still worked. Shouldn't they not work if they aren't in?

Also, to the far side of the fuse box (if you are standing by the drivers side fender), what are the empty spaces for? It looks like it holds other relays, but in my euro convertible, it has a metal pin that makes a circuit from one pin to another.

BTW, I'm in the process of trying to find out what makes the Euro spec models different from the US models when it comes to the operation of the fog lamps and being able t have them on while the brights are on or while the city (low beam) lights are off.

[Sean]

In general, a relay works by allowing whatever switch you use to power something - not have to actually FEED the power to whatever you turned on.

For example - I wired in my AC fan to a switch, so I could turn it on and off. I brought the 12v power into the switch, and then brought the power out of that switch directly to the fan. So, when the switch is activited, it runs the power THRU the switch. In some cases, a switch can be overloaded, and burn out. In my case, I'm using a 30 amp switch, which is connected to the battery with a 30 amp fuse put between them.

A relay makes it so that when that switch is activated, it sends a signal to the relay - basically a 12v source - at which point you also have a 12v source going into the relay's other "input" I guess you could call it. When the relay get's power into both the sources, it turns on whatever you switched on. When you switch it off, one of the 12v sources are dropped, turning off the device.

I really prolonged that explanation though. I'm sure someone can explain it in a lot less words. :)


PS: This is general, I'm not sure of your specific situation, but I was answering your very first question.

[AdamF 88iS]

You sure you unplugged the correct relays?

Relays are like electrically operated swtiches. They can do all sorts of stuff depending on what they are wired up to do. Some, like the fuel pump relay are used so that the DME can shut the fuel pump off without having to run the full power of the pump through those little tiny circuits. Instead it just has a trigger signal that clicks the relay on and off since the relay can handle more power. Others have timers, some act like fuses or circuit breakers. A relay is the reason the fogs wont run when the highs are on... it gets triggered to cut the fogs when you hit the high beam swtich.

[mph]

Alright, after doing some messing around, I'm still super stumped. The relays for the fog lamps and low beams are the same between the US and Euro models. However, the relay for the high beam is different. In the above pictures, you can see the Euro relay doesn't have a middle pin or even a place for one in the fuse box. But in the US model, there is a middle pin.

Also, the US model doesn't have the metal jumper next to the windshield wiper relay. There aren't any contacts in the slots. But in the Euro model, there is a jumper and several contacts in the slots of the fusebox.

I really wouldn't think there would be a huge difference between the US and Euro models. It would make sense that the difference between the operation of the fog lamps would lie in a relay, not the wiring itself.

Does anyone else have a jumper like the one pictured for my Euro cabrio in a US model?

BTW, the Euro doesn't have power steering or air. The jumper may be related to that, I don't know.

If anyone knows different or anything, please chime in.

[mph]

Ohh yeah, I forgot to mention. I tried switching the relay from Euro for the high beam to the US model. The fogs don't work at all on the US model without that middle pin.

[Bimmerfanatik]

Does anyone else have a jumper like the one pictured for my Euro cabrio in a US model?

BTW, the Euro doesn't have power steering or air. The jumper may be related to that, I don't know.

If anyone knows different or anything, please chime in.

My euro car has that jumper too - and it has no PS or air as well. Well, it has air, but it was added after, so I'll assume it was wired differently than the factory would, therefore for the purposes of this discussion, I think it's safe to say my car has no air too. :)

I'm pretty sure the fog light relay is the same, as I sold mine to someone with a US car and it works.

I've got a few US cars I can peek at - I'll see if there are differences.

[mph]

Any ideas?