What component is this?

Hey guys,

I need to use my brake lights on my car as fog lights, I've found a guy who makes these tiny PCB's but I'm not sure what the component in between is? (Looks like some sort of resistor?)

Here's a picture of the PCB:



If you need more info here's a DIY on how to install the PCB: https://www.internetwork.org.uk/fog/fogpcb.htm


Could anybody help me find this component? I could just buy it from my electronic store then and solder it myself. (It's only 5£ but I'm not from the UK so with shipping I'm at 20£ for just 2 components.


Cheers, Yannick.

These are rectifier diodes, apparently 1N400x (x stands for voltage rating and doesn't matter in this application).

Two comments:
- 1N400x current rating is 1 A, not sufficient for stop lights which have usually 20 W (12V/1.7 A) each
- I don't believe that the intended lamp operation is legal according to any vehicle lighting regulation

Stop lights are mandatory, must be always operable. Fog lights are optional.

Strangely enough I'm familiar with this mod. Isn't the intent to make the rear fog lights into additional brake lights? That's what the US folks were doing anyway since we don't have rear fogs.

The intent of the diodes is to allow the brake lights to power the fog lights, but prevent the fog lights from powering the brake lights. Maybe you're doing the opposite, but the logic still applies. You just want to orient the diode so that it conducts in the direction you want to current to be able to flow and ensure its able to handle the current as FvM mentioned.

Do you only drive backwards in the fog? In North America most people drive forwards and have fog lights on the FRONT of their car. Fog lights are usually yellow, rear brake lights are always red.
The diodes allow the fog lights to turn on when the ignition and side lights are on.
Side lights? Do you also drive sideways in the UK? In Canada it is fun to drive sideways on ice and snow.

In Europe, or at least in Germany, they have a rear fog which is a single red light on the driver's side. It looks like a brake light, but only on one side. From what I understand its the law there to have it on when its foggy out so other cars can see you from behind.

US versions of these cars often have provisions for a rear fog bulb, but its not wired, or missing the light bulb, etc. So sometimes US folks will wire it up to make it work as intended (with Euro head light switch which has provisions for the rear fog switch) or wire it up in some other way.

Sometimes i'll see an Audi driving around with the rear fog light on on a clear night (I'm in the US). I suppose some Audis came with functioning rear fogs for the US market and the clueless owner probably doesn't even know it exists.

Like TXBDan said in Europe it's obligated to have a working rear fog light so when there's a heavy mist/rain people behind you can see that you're in front of them. Thanks for the answers I can find my way from here.

Cheers :thumbsup:

I have seen a very low centered bright red light on the Scion sports car. I doubt it is a fog light, maybe it is a brake light?

That light is actually a rear fog light in the Japanese and Euro markets. In the US it's just a reflector.

I've driven a BRZ on track, great little cars.

I Think,there are no regulations to stipulate that a fog lamp must be a single light positioned centrally or in side as in side light so brake lights and fog light are not same in my opinion.I see some car use one and some use two.When there are two fog lamps and they are positioned beneath or as part of the rear light cluster, which is commonly the case, they are bright enough to be indistinguishable from brake lights.

There are of course regulations for vehicle lighting, international like and partially contradicting national.

The international standard that has been adopted in many countries allows one or two fog lights. A distance of at least 10 cm to stop lights is required.

In some countries, e.g. many EU members, fog lights are mandatory, the usage is restricted to specific weather conditions, in some country the usage is completely interdicted.