97 Explorer Heater Blend door

Cannot seem to turn the temperature down using the heat control. Any suggestions on how to check the blend door motor or what else would be the problem.
ONly way to get the unit to blow cooler air is to use max ac

Yup, it's the blend door. See this fix at
http://www.blenddoorfix.netfirms.com/
It works for a lot of users. It only worked for me for a short time and quit so when I took it apart I found the top of the door had broken right off so there was nothing for the pin to grab.