BF fans I need your assistance on issue that I am having. The Mode **** that controls the flow of air for the heat/AC is works for all the setting except for the Heater setting. That's the image of the guy sitting with the arrow pointing down. This is suppose to push the heat through the floor outlets. Apprently this is not happening. Can you guys tell me what I need to check or fix to make this operational again?

Thanks for all your help in advance.
Izzy207
1999 Blazer

 

Check the actuators under the dash. I believe they are still vacuum operated on 99's....since it affects only 1 setting, more than likely it's not one of the actuators themselves but 1 of the vacuum lines from it to heater controls. Either cracked or popped off. Maybe listen for a "hiss" when switching from one setting to faulty one.... back and forth enough for it to build vacuum and hiss it back out. Good luck, let us know how you make out!