I have a general question about the my 1999 Blazer. Since now that it is summer I noticed that hot air blows out of the lower vents even thought I have the thermostat set on cold. I was wearing flip flpos the other day and for some reason it was burning my feet. Is there a way to stop this or is this how the truck was built?

 

This could be caused by a weak blend door vacuum actuator. If you run a search you should find a listing of the vacuum hoses, actuators, etc. I have posted this information in a few threads.