I have a little +2S and it doesn’t blow warm air from the interior vents. I get warm air on to the windscreen but not through the main vents. Is this by design (ie: they’re fresh air vents) or is it broken? If it’s broken, how tricky is it to fix the sliders?
There is a flap at the bottom of the heater box that moves in order to redirect the airflow. I would guess that there is something amiss with either that or the linkage. To have a proper look it is dashboard out, although you might me able to undo the dashboard fixings and see if you can get clearance to get your hands in there.