Heat!! It's cold

I'm having a problem with the heater on my 99' Jeep Grand Cherokee LTD. The blower works but no hot air is coming out. I did the "Automatic Zone Control- on-board diagnostics" and I get a fault code of "54" and "56". The book says "54- left temperature door travel too large", "56- right temperature door travel to large". But I have no clue as to what that means or how to go about correcting this. Any ideas???:banghead:

Read and weep. Sorry.

http://www.wjjeeps.com/hvac_sub_assembly.htm

The Blend door actuator might be out, replaced it on my '96 because it was broke and stuck on cool and just would not move to let hot air through. On my jeep it's located on the passanger side in the front left corner.