Soon after I got my Blazer (2002 ZR2), I had the hiss of death. New TC vacuum switch, cleaned AT fluid out of vacuum lines and new heater control switch. I replaced all the vacuum actuators too. There has been a small issue since that has gradually creeped up on the aggravation scale. It's especially noticeable during the "heater" months...aka winter. I still get some hot air out of the defrost vents when the switch is in the floor heat mode. Do I have the actuator hooked up a little wrong causing the door to be slightly open or is this just a quirk these rides have? The hot air is very annoying to the face, especially the eyes due to drying them out. Anyone else ever experience this? Thanks.

 

The defrost actuator is the one with the red&blue vacuum lines. For air to come out the dash vents, no vacuum actuator is used....the default position.

So, only suggestion I have would be to remove the pieces necessary to access this actuator and with the engine running watch its movement as air flow position is switched between defrost and floor. May just need to bend a bracket or loosen actuator mounting screws to adjust travel. Could be the internal door has broken or the end has come out of its pivot spot.

My '02 is doing similar: floor selected and I have air flow out the dash vents...which is also annoying to my eyes. Time for me to take the trim panels off and see what is going on. Hopefully it is not the internal door that has broken. There is a current thread about fixing this.

 

Do you know which thread you're referring to about the fix?

 

Look for "98 Blazer No Floor Heat"