would low refrigerant in my A/C keep my car from having heat?

What is your question?

I have a 1990 De ville and the a/c unit needs to be recharged.The system runs but no hot air comes from the vents. I have no leaks. last year the heat worked fine with the exception that it wasn't very hot. Now I have no heat only cold air. Fuse(s) are good and I don't have a clue as to what's the matter, could someone assist me in getting heat?