Unidentified button in Z4 E89 center console

[SSovets]

Hello,

I recently bought a 2016 Z4 sDrive28i from a dealer in Germany and noticed a small button in the storage compartment that replaces the ashtray (see pic). It lights up green if pressed, but I don't know what it does. I think I heard a different whine of the AC fans, but I am not sure. I scoured the manuals and the web, but couldn't find anything, so I suppose this button is not something factory fitted (although the car was part of the "BMW Premium Selection" program, so I wasn't expecting any "artisanal" changes to it).

Does anyone have any idea what it could be and how I could check? Preferably without having to tear the car apart

[uuJIMtq]

Definitely after market. Kill switch? Does the car start with it on? Maybe just a fake alarm light?

[SSovets]

Definitely after market. Kill switch? Does the car start with it on? Maybe just a fake alarm light?

I only turned on (and quickly off) with the engine either on or off, haven't tried to start the car with it on, but I'm pretty sure it would start. Also, the car has an OEM alarm, so no need for the extra light.

[gr00ve]

I only turned on (and quickly off) with the engine either on or off, haven't tried to start the car with it on, but I'm pretty sure it would start. Also, the car has an OEM alarm, so no need for the extra light.

one way to find it is to trace the wires, then figure out, what could that be.

[SSovets]

I got some info about it, the dealer that sold me the car was able to contact the previous owner and told me it's a "parking heater" (translated from German, so the exact term could vary), which I need to unlock first (again translated from German by the dealer, whose English is not very good). I wasn't able to extract any more information about the "unlocking" that needs to be done first (do I need to code something, connect some wire, or just press the button?) or the manufacturer of the heater, nothing.

Now the difference in fan whine that I heard makes sense. I tried to start the car (cold engine) and see what I can get with the button light on and off, but the results were inconclusive; maybe the outside temperature was not low enough (it was around +6°C). Will try again in a couple days, when it gets colder.

Does anyone know who could be the manufacturer of such a heater, where it could be located, or what this "unlocking" could mean?

[uuJIMtq]

Engine block heater? Take a look around. Being from Florida I have no knowledge of this cold craziness
He may mean to turn the switch off. If it is a block heater, before running engine.

[SSovets]

As weather warmed up and I found some time to examine the engine compartment, I found the heater, it's a Webasto Thermo Top Evo 5 kW. Now what I don't understand is how to control it, as the one button I have inside does not seem to be enough since this heater can work in multiple model (parking-auxilliary), and my results have varied, but I don't know depending on what. When I started it once, the windshield has been heated and defrosted, but the next time it was freezing (actually snowed) and I tried that - the windshield stayed frozen and the fan was blowing lukewarm air inside the car. The manuals I have been able to find on the internet are of no help. Does anyone have any experience with retrofitted Webasto heaters?