Strange fog light and indicator behaviour on new mercs

[Diesel Benz]

The owners' manuals are full of liability related warnings. Of course the lights would go off if you "stop in the middle". At least my car does not blink lights off if I turn quickly over the middle "parking lamps" position. The lights control unit would see I'm going from auto to main beams.

I understand that there is a chance for confusion but since you are supposed to go all the way clockwise, I don't see room for turning lights off for a person familiar with the car. The one not that familiar with the car, should stop and read how the lights switch works, you cannot see it in the dark anyway (missing lights on the icons appear to be a safety issue )

I admit that I'm using main beams at daytime running lamp mode but I assume the mains would still switch off if I selected parking lights from the lights switch.

 

[Diesel Benz]

Do front fogs project a significantly wider beam close to the car than dipped headlights? I've tried it, and can't see any real difference in illumination out to the sides. And that's with the fogs on full power, which of course would be illegal as a cornering light in clear conditions

On all cars I've had, the fog lights' beam is significantly wider, and shorter than that of dipped head lights. Don't have any photos supporting this though. But the specific cornering light on the W221 makes an even wider beam to the side, compared to the fog lights.

 

[BTB 500]

I've moved the switch as quickly as I can, and the headlights do briefly go off and back on again. Which is not ideal on an unlit road.

Sorry but I've seen much better design on much cheaper vehicles from other manufacturers.

 

[BTB 500]

But the specific cornering light on the W221 makes an even wider beam to the side, compared to the fog lights.

Yup I have no problem with those, they're designed for the job.

 

[robert.saunders]

I've moved the switch as quickly as I can, and the headlights do briefly go off and back on again. Which is not ideal on an unlit road.

Sorry but I've seen much better design on much cheaper vehicles from other manufacturers.

Indeedy - as mentioned on another thread, the Mondeo keeps the headlamps on when moving the dial from auto to manual, thus allowing fog lamp control

 

[marcos]

I've moved the switch as quickly as I can, and the headlights do briefly go off and back on again. Which is not ideal on an unlit road.

Sorry but I've seen much better design on much cheaper vehicles from other manufacturers.

Mine definately have a delay and unless you are particularly slow or have no control of your hand it is almost impossible to switch the main beam off whilst moving the switch from auto over to on.
Maybe it's different on different models.

 

[BTB 500]

Mine definately have a delay and unless you are particularly slow or have no control of your hand it is almost impossible to switch the main beam off whilst moving the switch from auto over to on.
Maybe it's different on different models.

Mine has a delay from auto to off .. it takes several seconds for the lights go out if you leave the knob there. But the headlamps go off immediately you move from off to side.

It may well vary slightly from one model to the next, but having the foglights default to off each time you start the car (as some other manufacturers do) would be far better. Of course the heated rear window switch already works this way.

 

[Colin_b]

Do front fogs project a significantly wider beam close to the car than dipped headlights? I've tried it, and can't see any real difference in illumination out to the sides. And that's with the fogs on full power, which of course would be illegal as a cornering light in clear conditions

My SLk has the cornering lights, and they are useful in certain circumstances, slow tight corners or the like. Came with xenon lights, and it does look odd from outside the car.

They only work (on the SLK up to about 25mph, it seems)

And being a user of foglamps (lots of fog, and suicidal dull brown Herdwick sheep on(literally!) the back roads) I've noticed a drop in the headlights when you go from auto to front fogs.

 

[gl boy]

There are a few previous threads on this ... technically it breaks UK law, where you're not permitted to have front or rear fog lights on unless visibility is under 100 metres. To avoid this some models allegedly change the light output when the foglight is being used as a 'cornering' light ... so it doesn't count as a foglight any more.

Personally I think it looks daft, and serves no useful purpose. On my in-laws' (German) R Class it seems to be triggered by steering angle rather than the indicators.

on my GL it works on the steering angle or when you but the indicators on under a certian speed... but do agree about looking stupid ,when parking in a carpark some one came over and told me that one of my spotlights wasnt working(never said why have you got you fog light on when its not foggy ) and i had to explain what was what with them

 

[slik_sly]

i have to say, the fog light being on while indicating really bugs me!! its the same on the new renault clio!

 

[BTB 500]

Got my mum in law staying at the moment, and we're moving her R Class out into the road every morning and back onto the drive every evening (having some fencing & paving done) ... so I'm getting major exposure to those lovely cornering lights this week. They look even more stupid when it's basically broad daylight and they're operating (I guess because the auto headlights have come on).

 

[oldcro]

Intelligent lights

My new C320CDi Elegance has intelligent lights and in auto mode the dipped and fog lights come on together. I cannot switch the fog lights off without switching to dipped beam. I like the idea as it gives a good spread of light to the front sides as well as ahead (hope that makes sense). However I am not sure of the legality of driving with fog lights on when it is clear but just a bit dark.

The only gripe I have about the car is the horn. To sound the horn takes a firm push on the wheel padding, as there is very little room left for using your thumbs due to the groups of buttons each side. This makes it difficult to give a friendly toot toot to someone ( Living on a single track road with passing places requires lots of toot toots when someone driving towards you pulls in for you, and vice versa). I usually end up giving a beeeep as if I was annoyed with them rather than thanking them. Hope I learn to just toot toot before I am forced to move house.

 

[Diesel Benz]

My new C320CDi Elegance has intelligent lights and in auto mode the dipped and fog lights come on together. I cannot switch the fog lights off without switching to dipped beam. I like the idea as it gives a good spread of light to the front sides as well as ahead (hope that makes sense). However I am not sure of the legality of driving with fog lights on when it is clear but just a bit dark.

This sounds really odd, at least there needs to be an option where the fog lights do not come on automatically. It would be illegal in many EU countries if there is no fog or heavy rain.

There was already a warning against hostile comments on using fog lights when there is no fog but I could not resist since the description above about the light pattern to the front. The big disadvantage of fog lights is that they only cover the close range in front, in normal conditions the light pattern should be the opposite, beams having higher density further away in order not to blind eyes from the higher density closer.

At heavy fog one would be driving slower and no lights would reach far, then it is better to have intensity closer and less reflection from the fog.

The above is the negative part for the driver itself, even if it may feel like the lights were better when fogs were on. There is another negative issue with fog lights and that is for co-drivers approaching one with fog lights. Fog lights are placed low (in order to have less reflection from the fog back to driver's eyes) and the angle to the road is lower than main and dipped beams, this makes a wet road reflect a lot more light to others' eyes. I'm really ****** off with these drivers "showing off with their fog lights", making driving worse for both. If you had eyes of one who just got the driving license, it may not be as bad approaching one of these but the older you get, the more reflections disturb your view (you may read some experience, for once it would be nice to have less experience ).

 

[whitenemesis]

The fogs (F&R) will only operate with the switch set to "Main"

Switching from "Auto" to "Main" does not switch off the headlights even briefly.

 

[BTB 500]

The fogs (F&R) will only operate with the switch set to "Main"

Switching from "Auto" to "Main" does not switch off the headlights even briefly.

I assume you're talking about your specific car.

On my Vito the foglights operate with the switch on Main or Side, not just Main.

And as already mentioned, the headlights do go off when the switch passes through the Side position.

 

[BTB 500]

I checked my SL when fitting new bulbs this morning, and the fogs operate with the light switch in the Side position on that too. No auto lights on that car though (just auto wipers).

 

[glojo]

The law always used to be that if two foglights are fitted then both lights had to come on?

We have the older active headlamps and it is not all that good. The bi-xenon's are simply too good.

Regards
John

 

[MBManInKen]

At night the headlights most definitely do go off as you pass through the 'side' position on your way from 'auto' to 'main'. I've tried it, and I don't like it!

OK, I now had a chance to try this on my car yesterday. When the lights are on, going from auto to main, or further to both fog light positions, does not turn the main lights off. They stay on. Same for the opposite direction (from fogs or main to auto via side beams). The main lights stay on during the transition.

Unless I am mistaken, the actual operation is a software affair, the switch just signalling what you want, rather than being directly electrically connected to the lights (well, at least on my car). It appears that the software does retain the configuration at least for a short while as you are turning the button, which makes sense.

If you turn from auto or main to side beam, the lights initially stay on, then if the switch stays in side beam, after a pause the main lights will go off.

All of this is exactly as I would expect it to be.

On the other hand, we have often shown different behaviour between different Merc models even of the same year, so I'm not holding up my hopes that the above will apply to everyone's car .

 

[DansSlk]

Its just a software thing with BTB's mota, no idea why they would design it like that but there you go.

Some of the manuals do warn that in foggy conditions the lights should be activated manually before starting your journey because the operation of the light sensor cannot be relied upon and i can personally confirm that, so maybe the thinking was if fogs are needed the lights would be on manual anyways.

Bad plan really since we often drive into fog.

 

[MBManInKen]

Yes, on cars like mine, if you're in fog, you have to abandon auto mode in order to switch the fogs on.

One obvious problem that I can see in automating fog lights is the tricky problem to identify when it is foggy. That is not an issue of light level, rather of visibility, transparency. I'm not sure how you would build a sensor for that .

Light-dependent resistors are simple things. But how would you build a fog identifying component?