I still have such a merc, complete with the button and message in question. I think that implementation is actually not so bad, since you could just purchase th

I still have such a merc, complete with the button and message in question. I think that implementation is actually not so bad, since you could just purchase the BT module and install it yourself [0], without having to mess with the infotainment system or the steering wheel, which also has phone buttons that behave the same. Whereas here, if the multi-zone AC system is actually not physically present, it may be somewhat more involved to upgrade on your own. --- [0] It's a Bluetooth module supposed to go in a compartment in the arm-rest. There's already a connector present. But since I don't care to use my phone in my car I never purchased the module, so I don't know if the full wiring is in place and if the radio would use it without fuss.