The heater core is located in the black plastic plenum that is usually visible under the dashboard and also from under the windshield when you raise the front hood. The heater hoses usually enter from under the front and the heater control valve is usually there also.
Cable controlled heater valve.
When fully closed, feel the two hoses as they enter the plenum and they shouldn't feel hot. Many folks install a manual ball valve in one of the hoses to stop all flow of coolant when heat isn't needed. Every school bus I ever drove or owned had these valves added to reduce the heat in warmer months.
Linear Mode
