I have seached the forum for a couple of days, if I have missed this question I apologize. Recently bought a '92 S-10 Blazer. The heater doesn't blow, but when I adjust the heater control the compressor wants to cycle off and on. The person I bought it from bought it to turn it so he knows no history. Also the horn and doesn't work, the fuse seems good , wasn't sure if the 2 were related

The horn is next to the drivers side headlight.It has a green wire check there to see if it is connected and pop off the horn cap on the steering wheel and see if you are connnected there.

if you put the heater controls to defrost, it will use the AC system to dehumidify the air.

This is normal.

I have seached the forum for a couple of days, if I have missed this question I apologize. Recently bought a '92 S-10 Blazer. The heater doesn't blow, but when I adjust the heater control the compressor wants to cycle off and on. The person I bought it from bought it to turn it so he knows no history. Also the horn and doesn't work, the fuse seems good , wasn't sure if the 2 were related
Early Winter 2004 My Chevy Blazer 4x4 had a problem with the Heater Core
and I replaced the thermostat and the dexron coolant. It solved the problem
with the heater. ( The entire week of February 1 it was 2 degree's below zero)
The new Trailblazers have the best cooling and heating compaired to the
older Chevy Blazers. My bothers 2004 Trailblazers heat is so hot you have to crack a window open. I'm lucky just to get 80 degree's even after running the
car 4 hours on the highway.