When my 7.5 has been sitting in the sun all day at work I can hear the small fan some where behind the dash going very fast for a very long time, I guess to cool the AID and infotainment, I do wonder if I'm supposed to be able to hear the hum from it as it makes more noise than the main AC fan.
To me it would make sense to divert some of the AC cold air to behind the dash to aid cooling as I can imagine that's it's roasting being in the full sun (bit like the glove-box cooler).