Little Hole on bottom of rear view mirror..

[Geoff]

Am a newbie here and have just taken delivery of a C220 CDI Avantgarde SE Automatic. I've already upset a few regulars by daring to suggest that I might use an automatic car wash, so hopefully the next question is a bit less contentious !!

I'm trying to figure out what all the various sensors are for heating, lighting, etc but there's one that I can't figure out. On the bottom of the rear view mirror there is a little hole which has a kind of orange light glowing out from it – what is this for ? I am assuming that it's nothing to do with the auto dipping mirror as there is already a little sensor in the mirror glass for this, so what exactly is it for ?

Also, the automatic headlight function is good, but so far I've only ever experience it switch on the dipped headlights, even when it seems relatively bright outside. Should it also activate only the sidelights if the light sensor decides that dipped headlights are not necessary ?

 

[Shude]

It's ambient lighting for the dash area.

 

[Flash]

As far as I am aware (on all my W203s I ahve had) when auto lights kicked in the dipped lights would always actiavte and never the small side lights.

The light sensor is located in the windscreen (black box) and so is the rain sensor for the wipes (if u hav ethat option).

The light sensor is quite sensitive (if adjutsed to full sensitivity by the Stealership) which mine is as was replaced not that long ago.

flash

 

[Geoff]

Shows how much I know, as I thought that the light sensor was on the middle of the bonnet, in between the two washer jets. If that one isn't the light sensor, then what is it for ?

 

[Flash]

I initially though the same as you - my headlamp locators were not function corretcly and often failed at night - Stealer advised that elements of the sensor are located in the black plastic box that sits in the centre of the windscreen and after replacing this compnent all was then fine with my headlamp locators.

Try this test out - activae ur headlamp locator settings from software menu, cover the black box that is mounted in the centre of the windscreen with ur hand (from outside of the car) and then lock/unlock ur vehilce. U will find that the headlamp locators function/come on . Do the same to the black ball mounted on the air vents on the bonnet and u shall find that the headlamp locators do not function Off course this will have to be carried out in broad daylight - this exercise/test works on my car but my sensor has been adjusted to full sensitivity by Stealer as uuto lights function from the shdow of buildings in broad day light/slightest bit of cloud)

Flash

 

[Shude]

so what is that stupid bonnet thing then?

http://mbclub.co.uk/forums/showthread.php?t=3202

 

[Flash]

Have no idea now and I too initally thought that it was the light sensor (however, if u carry out the test/exercise that I have decribed in my previous post) then this contradicts the theory that the light senor is the ball on the bonnet unless they ball on the bonnet is linked/component of the light sensor that has elements ont he black box that is mounted on the windscreen. My entire balck box was replaced with a new one and reprogrammed.

Flash

 

[Shude]

Hey, what would I know, but...

Is that why when i cover my sensor on the bonet that the headlights come on

 

[Flash]

U should become a Lawyer Shude... (I am very impressed...)

Honestely, (hand on my heart) - my theory works and when I cover the sensor on the bonnect (the ball) nothing happens - could it be that our cars have different build dates? The black box on my car ahs been updated with the latest one i was told.

Be intersting to see the results if all W203 owners (especially 2004 onwards were to carry out the test with covering the black box with their hand from outside the windscreen and then the black ball on the bonnet). Please post back ur findings

Flash

 

[andyw]

you mean i have to go outside (again) and do something with my car that will provoke the usual questions from my work collegues?!

oh ok then

 

[Geoff]

I'll try out your test Flash, on both the windscreen sensor, and the bonnet sensor, and let you know the outcome !!

 

[Flash]

Cheers Guys...

Flash

 

[Shude]

Like I said, wtf would I know I don't have a light sensor on the bonnet or the windscreen, I'm only quoting other people

 

[andyw]

auto headlight sensor definantely on windscreen

no idea what little "ball" is on the bonnet grill - are we sure it is a sensor?

 

[Flash]

I know ur only quoting what someoe else was saying but I too could be wrong or even have some sort of glitch with my car that the monkeys at the Stealership have messed up. Ur a very knowledgebale person Shude and know way more then I do and I would not dare contest u .

Flash

 

[Shude]

no idea what little "ball" is on the bonnet grill - are we sure it is a sensor?

What else could it be? It's definitely not a styling thing is it?

 

[Flash]

I know ur only quoting what someone else was saying but I too could be wrong or even have some sort of glitch with my car that the monkeys at the Stealership have messed up. Ur a very knowledgebale person Shude and know way more then I do and I would not dare contest u .

Flash

 

[Shude]

Ur a very knowledgebale person Shude and know way more then I do and I would not dare contest u .

I was under the impression that the sensor in the glass is for rain and the one on the grill is for light.

Do all W203s come with auto headlamps and auto wipers?

 

[Flash]

auto headlight sensor definantely on windscreen

no idea what little "ball" is on the bonnet grill - are we sure it is a sensor?

Cheers Andy - ur the man!!! (at least I know that there is not a fault with my car now...

Flash

 

[Flash]

I was under the impression that the sensor in the glass is for rain and the one on the grill is for light.

Do all W203s come with auto headlamps and auto wipers?

Auto headlamp is standard on all W203s but rain sensing wipers are extras...

Flash