i have a 96 s10 blazer.with ac on in any ac position air is blowing only through floor and dash vents.doesnt matter what position switch is in only blows through those two places.when not using ac air blows correctly in all other positions (vent,floor,defrost,defrost/floor).truck has manual hvac controls.thanks for any help.LARRY

 

I'd say its probably a vaccum leak, but im not an expert, all i know is that i have a vaccum leak that i need to fix and until i do... my A/C only blows on medium, and theres a constant sucking sound.

 

Maybe I can respond now that someone else has.

Yes, it is definitely a vacuum problem to the HVAC module. Is the truck 4wd?

 

yes it is.