Strange fog light and indicator behaviour on new mercs

[DansSlk]

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?

Yeah its a bit more tricky.

I've had lights not activate in fog on various MB's I've had but I've actually had the lights go out on another car I own.

But it was just a case of pushing a button to reactivate them because BMW tie the lights together on auto.

 

[whitenemesis]

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 .

Exactly as I found on my car

 

[robert.saunders]

I tried an experiment this weekend just gone. I didn't leave the lights in AUTO mode.

What happened was not only amazing, but actually outstanding. When it was dark, I switched the lights on. When I had finished my driving, I switched the lights off. I found it really liberating.

Sadly, it wasn't foggy at any point during my experiment, BUT, I'm sorry to say - I did activate my front fog lights, not only when my side-lights were on, but also when my dipped beam was on. It worked a treat.

Then I switched them off again.

Conclusion? I seemed ok to activate the lights through my own ability. I expect if I drive into a tunnel the auto-lights may be quicker than me, but surely I could see the tunnel coming? Sadly there aren't many mountains in these parts, so I didn't have any tunnels to practice