my 93z28 would warm up to the normal operating temp. the heat does work but it like luke warm. what could cause this to happen. i have replace the themostat with the 180 hypertech stat. i have a hypertech chip install as well. i dont think that could cause it to do that but i could be wrong.

 

Colgged heater core, air doors stuck, low coolant level, engine running cold, (check gage).