automatic climate control no heat

i have auto climate control,alldoors work air goes where it suppose to a/c works excellent but no heat no matter what temp you set it on. also noticed when a/c fan and mode in auto car cools off but fan does not cut off as if it doesnt know what temp it is in vechicle. any suggestions

check out this post
http://www.automotiveforums.com/vbulletin/showthread.php?t=456009

for heat most commonly it is just a flush is necessary because the crud builds up in the heater core. on that note, just hope it isnt the heater core, try flushing it with the prestone flush kit

kit+water+radiator flush+ Radiator Fluid will maybe run 20bucks