Hi. Out of boredom, i started to read the manual for my aftermarket radio and realised the reason night mode does not work on it is because it's hardwired into the dimmer function. That's an orange/white wire that goes into the first adapter then connects to nothing. 

 

Now, on my facelift fabia, there's only 8 speaker wires, constant voltage, ground, can +/- and that security wire thing. Closest wire that does something when headlights come on is the rear demister button.

 

My question is, has anyone tried it before? Does it work tapping into the backlight of a button?

 

if your asking whether your radio will dim at night (or to be more precise when the  lights are switched  on).............................. if you tap into a feed from any switch illumination, the asnwer is yes, all the radio needs to see is a feed from a light source / feed.