Outside rear-parking lights turn on for that function (on 2001-2004.5 models) not the inside lights.

2005+ models have both inside and outside rear as parking lights (and the inside driver in US is a dual filament bulb to allow functionality of the rear foglight).

i made the exact same mistake when i first got my car, but i asked my mechanic before actually getting a new bulb

made me feel real smart.....


he said german cars are usually the only ones that have just one rear fog, anyone know how true that is?

lol...well I felt pretty stupid for a few minutes, but all in all, its a funny mistake....and like I said at least I have some extra bulbs if I need 'em, only $3 anyways...it was a quick look and immediate judgment thing, like oh my god I gotta get it fixed! so I went straight to pep boys

It must get really foggy in European countries or something...

As far as having two rear fog lamps, the R171 can be version coded to have both sides come on or just one. The guys in Germany said that was done for places where the law states that all lights have to be symmetrical.

I think there is a state in the Northeast that requires symetrical lights, but I'm not 100% sure.

It is.

that makes sense because i was wondering why the passenger tail light would have a fog bulb if it didn't light up lol

That is the exact reason I went crazy and straight to pep boys, it didn't make sense to me, lol

Yeah i freaked out too, then my uncle avid Audi/Porsche owner told me about it. Felt kind dumb for a sec - wondering why the hell both switch lights came on. Such a newbie.

if u had the S-Class tail light u can Rewire the rear Fogs so that it lights up with the Parking/city lights like the 2005+ C Class see my pic below u can see it alittle

I do, but i dont understand what your saying ? Please explain ?

ok look at this picture notice the entire bottom row of lights are lighted up.. does yours light up like this? ..meaning the regular lights and the Both REAR fogs are lighted up do u understand?

ohh this Is Franks car

I dont think both my fogs light up, Imma try that this evening. But im almost sure both dont. How would i make both light up ? or is that something just in the wiring with the s-tail/ w leds ?

Keep in mind, you lose functionality of the rear foglight with the way this was wired.

I think I've figured out a way to keep the functionality of the rear fog and have both running lights as well. And it involves more than just wiring (not much more), but requires more parts (small amount of $$).

Fill us in with the info drex.. with what Extra parts will be needed.

You have to Rewire the Fog into the rear light for this to work and it can be done with the LED or the NON- LED Version of the S-Class taillights

For sure. Once I get it done (i.e. when I'm feeling less lazy), I'll even post pics. I'm not 100% sure that it is going to work, but I can't think of any reason that it won't work.

In fact, I'm going to see if I can get dual rear fogs.

PS...be patient with it guys (just keep your eye out for my post when it happens). I've been wanting to sit down and do this for over 1 year and just haven't had a chance AND have been too lazy.

2nd. I have the led version - so please give both examps.
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Wow, am I glad I came across this thread. I recently learned that my car had rear fog lights, so I turned them on, only to see that only one turned on...

I thought I had another light out haha...