Exterior but no interior lights?
Weird one today with the light and rain sensors. My previous A3 had only the light sensors and I'd often find that it wouldn't switch the lights on in heavy rain as there was still enough ambient light to prevent it. No problem, I just had to switch them on manually in such situations.
With the rain sensor on the new one, the car not only uses this to trigger the wipers but it also contributes towards the triggering of the lights, so when it's raining the lights will be switched on at a higher ambient light level than if it were dry. Apparently this is no uncommon for cars with both light and rain sensors and obviously makes sense.
Today however, I had something really weird. Driving along the M6 in torrential rain but adequate light, I noticed that the exterior lights were on but none of the interior ones were! No dashboard or instrument illumination and the interior light pack LEDs weren't on either. What I'm wondering is whether this was the system being clever and realising that the exterior lights were only being triggered due to the amount of rain rather than lack of light and so the interior illumination wasn't needed? Or, more likely IMO, the computer just had a brain-fart and "forgot" to turn the interior lights on :)