Hi Donna, before you start messing with the switch check the heater hoses under the bonnet, they are the thin rubber hoses that run from the back of the engine into the car.there are 2. does your temp gauge work? It could be the Thermostat, Is there water in the system? go fo these first if all I have menstioned is well then go for what you have stated but I think the control will be right, On a futher point has the car run out of water or a heater hose cracked / broken? If so you may well have an air lock in the system that will require bleeding.