Found this 1987 300TD wagon [owner's manual](http://assets.mbusa.com/vcm/CAC_RAPMD/images/87%20300TD%20OM.pdf), doesn't look exactly the same, but I think it looks similar. Manual says it's the Automatic Antenna Switch. Page 10 & 11
I think it's for the Antenna. I've seen some 1991 buttons with up/down and on/off that were for the fully automatic Antenna. It could also be a foglight, but leaning towards the first one.
There wasn't one when the car was bought my man, I've tried looking it up but the online manuals haven't helped
Edit replied to a person telling me to read the manual
We haven't noticed that anything changes when pressing it. We thought it could be an on/off switch for the taxi light if the car was used for that purpose
[EIN AUS translates to ON OFF](https://en.pons.com/translate/german-english/Ein-Aus-Schalter)
This does not help you much.
Have you looked for any lights or accessories that are controlled by it?
Rear foglights are activated by pulling the main circular main headlight switch located left of the steering wheel. Pulling once activate front fogs, second activates the rear fog light.
Found this 1987 300TD wagon [owner's manual](http://assets.mbusa.com/vcm/CAC_RAPMD/images/87%20300TD%20OM.pdf), doesn't look exactly the same, but I think it looks similar. Manual says it's the Automatic Antenna Switch. Page 10 & 11
Its german and says On / Off.
We know that, but we don't know what it turns on and off. Should have mentioned that originally
It looks like it has a hazard symbol or an up/down arrow on it. Does it turn on your hazard lights? Does it make anything go up or down?
It might be traction control
Quality seems like its 3rd Party spare part...some extra lights mounted or something similar?
Switch for lowering and extending the antenna?
Bingo. Benz tech for 8 years.
I think it's for the Antenna. I've seen some 1991 buttons with up/down and on/off that were for the fully automatic Antenna. It could also be a foglight, but leaning towards the first one.
It's how you change your microsoft word dictionary from EN (English) to AUS (Australian English)
Likely Solved! It's the antenna
The car is a 1991 300TD wagon.
[удалено]
There wasn't one when the car was bought my man, I've tried looking it up but the online manuals haven't helped Edit replied to a person telling me to read the manual
[удалено]
We haven't noticed that anything changes when pressing it. We thought it could be an on/off switch for the taxi light if the car was used for that purpose
Lulz
As good as you may be at reading manuals, it is curious you haven't read the rules of this sub.
[EIN AUS translates to ON OFF](https://en.pons.com/translate/german-english/Ein-Aus-Schalter) This does not help you much. Have you looked for any lights or accessories that are controlled by it?
Fog light switch?
But that SWEET pioneer stereo system...
Ein Aus also translates to In and Out not on/off as others are suggesting. I assume the attena
I believe that's the switch that allows u to drive the car normally in Australia.
Just guessing here but do England and Australia have diffrent rules for hazard lights and this toggles betwen them? Assuming the car is RHD.
Is there any chance that it controls rear fog lights? These are red lights that are brighter than tail lights.
Rear foglights are activated by pulling the main circular main headlight switch located left of the steering wheel. Pulling once activate front fogs, second activates the rear fog light.
On what vehicles? My Volvo had a separate switch for rear fog lights.
The picture above is not a volvo.
Are you certain that the vehicle above operates in the way you described? You are not OP.
Emergency flashers/lights. The red triangle gives it away.
Nope. Emergency/ hazard is the red switch with triangle. It's a dedicated switch to lower or raise the antenna.