Volvo xc70 climate control system

My air conditioning system works perfectly, ie blows cold air, for a while (app. 40 min) then it doesn’t blow cold air any more (seems like the cold air is diverted to the dashboard). But if I turn the blower fan off, wait for 3 min, then turn on the blower again, it would blow cold air again. Any idea what’s the problem?

It sounds like there is a problem with the vent doors. I’m not sure if yours are controlled electrically or with vacuum air.

How do I find out?