I did a search and couldn't find anything relating to this problem. I'm about to replace my heater core anyway so if it's something I could do while the rest of the dash was disassembled that'd be wicked. Thanks for the input guys.

 

Wow, it's discussed EVERYWHERE!!!

1st thing, check your vac hoses that go from the heater box to the globe looking thingy under the hood on the passenger side.

A tell tale sign that one of those are blocked or cut. Give that a try first.