front defroster blows cold

previous owner to my 96 sub mixed coolant and sludged up all components, so i just finished changing most components. after checking controls i found 2 things. 1.my front defrost will only blow cold air. 2.my heater valve (new) doesnt seem to switch on. during which cycle should the line be pulling vacuum. i pulled top vacuum line of actuator and am getting good suction. is actator bad? is there a vacuum line that may switch the defroster from hot to cold?