Heating.. Help?!

Hey guys, so my father has a Omega B VFL, with automatic air conditioning the air conditioning works perfectly gets cold and everything around it and so the heating doesn’t work at all you can drive around half an hour on HI and it doesn’t get warm. If you press ECO also nothing changes, from the ventilation comes a bit of lukewarm air but never enough to make the interior really warm. Does anyone have an idea what that could be and where the problem lies? us ks18419