I'm trying to imagine what the "click/clack" would be. As near as I can figure, that was your blend door cycling due to a bad temp control vacuum switch or vacuum actuator. The noise was the door moving back and forth from heat to cool and finally failed and I believe the default position (with no vacuum) is cool. Check to see if you have vacuum at the blend door actuator with selector switch in the floor heat position and temp control in "hot". If no, move the blend by hand to see if you get heat. If you get heat, the actuator is bad. If no vacuum in heat or cool position, the temp selector control is bad. Hope this helps.
Dec 20, 2016 at 6:08 PM
