jl9j

Hey all,

It was raining and foggy and I was going over the mountain, so I decided to turn my fog lamps on. I used both the front and back. When I passed a fellow C class, I realized there were no fog lamps in the rear. So when I got back home, I had a friend pull the switch on and off while I stood behind my car. Apparently, when you pull the switch for the 'rear fog lamps,' what you get is your tail light becoming brighter. However, only ONE of my tail light became brighter (driver side)! Is this normal? Is only one of em suppose to 'work?'

TheDarkSide

Yup, thats normal. Only the drivers side becomes brighter.

MBnewby

it's a weird euro thing...had a friend ask if i had a tail light out...

jctevere

Yea, I don't really understand why they did this. For years I thought MB had such a electronic issue because I always used to see one light brighter than the others, turns out, only after I own one myself, that this is normal. I still think that they should just allow both to get brighter? I'm sure I wasn't the only one who thought that a massive amount of MB had this problem and have been turned off from the brand by it... haha.

But now that I am thinking, maybe there is only one that turns on, because if both were on, people wouldn't notice that your braking as easily?

jl9j

I guess it makes sens that only having one light up attracts more attention.

Beausoleil

Yes. It's not all that uncommon to find just one rear foglight. Attracting more attention is one thing but these days when manufacturers are boasting about their LEDs being more energy efficient than halogen and tungsten bulbs, it makes sense that no more lights than are necessary are fitted.

Many cars have a foglight on the driver's side and a single reversing light symmetrically opposite. In the far east, where they generally don't fit foglights for the domestic market, cars bound for other markets often have foglights added to an export specific bumper or other location outside the main light cluster. I had a Nissan 300ZX TT in the UK years ago which was spoiled, IMO, by a pair of foglights recessed into the rear bumper but at least it was a pair. The Honda Prelude just had one light off to one side.

blue00r6

I would imagine it's so they don't get confused as brakelights

phatboypimp

From our friends at wikipedia....

In Europe and other countries adhering to ECE Regulation 48, vehicles must be equipped with one or two bright red "rear fog lamps" (or "fog taillamps"), which serve as high-intensity rear position lamps to be energised by the driver in conditions of poor visibility to enhance vehicle conspicuity from the rear. The allowable range of intensity for a rear fog lamp is 150 to 300 candelas,[15] which is within the range of a U.S. stop lamp.[5] For this reason, some European vehicles imported to the United States have their rear fog lamps wired as stop lamps, since their European-specification stop lamps may not be sufficiently intense to comply with U.S. regulations, and in North America rear fog lamps are not required equipment. However, they are permitted, and are found almost exclusively on European-brand vehicles in North America — Audi, Jaguar, Mercedes, MINI, Land Rover, Saab and Volvo provide functional rear fog lights on their North American models. The final generation Oldsmobile Aurora also had dual rear fog lights installed in the rear bumper as standard equipment.
Most jurisdictions permit rear fog lamps to be installed either singly or in pairs. If a single rear fog is fitted, most jurisdictions require it to be located at or to the driver's side of the vehicle's centreline — whichever side is the prevailing driver's side in the country in which the vehicle is registered.[15] This is to maximise the sight line of following drivers to the rear fog lamp. In many cases, a single reversing lamp is mounted on the passenger side of the vehicle, positionally symmetrical with the rear fog. If two rear fog lamps are fitted, they must be symmetrical with respect to the vehicle's centreline.[15] Proponents of twin rear fog lamps say two lamps provide vehicle distance information not available from a single lamp. Proponents of the single rear fog lamp say dual rear fog lamps closely mimic the appearance of illuminated stop lamps (which are mandatorily installed in pairs), reducing the conspicuity of the stop lamps' message when the rear fogs are activated. To provide some safeguard against rear fog lamps being confused with stop lamps, ECE R48 requires a separation of at least 10 cm between the closest illuminated edges of any stop lamp and any rear fog lamp.[15]

jon3sh

Canadian models are the same too just driver side.

Carzzz

It doesn't look good with just one on... The C-Class rear fog should be symmetrical!

B AS IN BENZ

This means that the drivers side bulb is a dual filament right? Could it be that the passenger side is only a single? But if you stick a dual filament in there it might work?

I have to find out.

Wierd, my GF told me that one light was brighter than the other a couple of days ago following me home.

Wouldn't CHP think that your bulb is out and pull you over for this?

RLE

.....

keith100

Exactly - its to tell an approaching driver the difference between a simple warning foglight and braking lights.

Stone2486

It's not a dual filament, its a single and all thats changed is the voltage to the bulb. It's electronically controled by the rear SAM when the switch is on for the rear fog.

K-A

I get so endlessly annoyed when dingbats drive around with the rear fog light on. It looks bad (like a light is out), and doesn't help M-B (or whatever car it's fitted to) look good to boot.

I think Euro makers should just discontinue the feature for U.S buyers. Most have no idea what it is, and the Dealers sure don't tell them. It probably causes more annoyance and problems then it does help anyone in fog.

hannes

The German highway code only permits using the rear fog light in severe fog (simultaneously prohibiting driving any faster than 12 mph).
It specifically prohibits using the light in the rain (though the law differs in other jurisdictions, Belgium, I'm looking at you...).

Using the rear fog light when not necessary (light fog, no fog, rain) is distracting to other drivers. Particularly in the rain/snow when the light is being reflected it is a safety hazard to continuously have a very bright light in front of you.

The fact of only having the light on one side of the car sort of underscores that "exceptional circumstance" purpose.

RLE

I posted this info a while back (minus the SAM info) on another thread on this same subject.

Except I discovered the two voltages with my Fluke meter while attempting to convert both rear fogs to extra brake lights which I have done on nearly every past MB. So, it can't be done due to technical reasons.

Our cars are country coded which means that to move the rear fog to the right or activate the flashing brake light feature, as two examples, the car's base configuration must be changed by the tech's laptop and a disc. Maybe even connected to MB Germany such as when the Telematics updates were being done a few years ago.

This info came from my dealer's service manager when I asked about flashing brake lights.

Peabody

You're only supposed to turn the rear fog on if your visibility is less than 50 meters. So if you think it looks stupid, you probably shouldn't be turning it on to begin with.