heater and a/c problem

[tack87]

I just bought a 02 exp a few months back. When I went to use the a/c it worked in the back, but it wouldn't always work up front. Now that it got cold out I tried the heater and once again it works in the back but not at all up front. I am at a loss here, I haven't a clue what the problem could be. Any help would be great thanks.