My truck has an awesome heater but the sucky thing is that it doesn't blow on the floor... where I like it best. When I put it on the floor setting or the floor/defrost setting, it just blows defrost (windshield). Anybody know why this happens or how to fix it?

 

check all vacuum hoses under hood would be a good start

 

If you are changing from the dash to defrost then it's most likely the selector switch or one of the vacuum actuators that is bad.

 

had this happen to me, it is a small plastic damper in the plenum just behind the ash tray, they brake at the neck and then will not rotate into position. there is an easy way to fix this.

this thread covers this.
https://blazerforum.com/forum/2nd-generation-s-series-1995-2005-tech-41/98-blazer-no-floor-heat-17808/

just recently someone on here fixed this without cutting, i believe they removed the center console on the floor and then the small plastic channels that connect to the ducts on the floor and was able to put there hand up in the ducts and swap out the part.

do a search on no floor heat, this seems to happen alot to our rides...plastic gets old and brittle then snaps in winter weather.

good luck.