my 02 liberty only blows cold air,replaced thermostate,waterpump & blower control mod.i use to get heat but only when selector knob was just past the half way mark,,now only cold air blows,,

heater issue started last year,heat would only blow when i put the temp dial in the just past half mark,the closer to max hot the less heat would come out.this year i changed the thermostate,waterpump & blower control mod..but before i changed anything i lost ANY heat function that i had prior with the temp control knob in the half way position,thats why i replaced the 3 item's that i listed..