Can't stop the heat

Hi Guys (&Girls) I have a1998 4.3 Blazer LS loaded. with climate control. the problem is that I can't shut the heat off. Constant heat rolling out I can switch vents and havn't found any vac leaks. I search the forum and found nothing. I Have three other friends that have the same prob. I can't find the temp control valve in the hose either( or I would turn it manualy. any help is appreciated.

Needs to be put on a HAVC/Body heater control mcapable scanner.
Check for codes and post back any codes.

Also pull RDO/BATT FUSE check fuse and for power to it and reinstall.

After pulling and installing the RDO/BATT fuse key off turn key on and start engine.
You should hear and feel the actuator motor cycle hot to cold or cold to hot.If no check the actuator motor and door.
Let us know what you find.