The heat will only blow on the defroster sometimes it will switch to the floor but thats once in a great while. Any suggestions?

 

You have a vacuum leak. Search for vacuum leak, and you'll find a bunch of different posts where people describe where they found their leaks. It can be hard to track down, but there are a few common places to start with first.

 

in the vac lines on passenger side near firewall is a check valve. its smaller than a penny only about 3/8" thick. it can go bad. there is also a vac resovoiur under the black plastic cowl on passenger side. it holds a generous supply of, well, nothing.....