Heater will not work

My heater will not work. I have checked the power all the way to the switch and have power all the way back to the blower fan. I have even changed the switch. It has come on all by itself, but if you just flip the switch, no-go. How do you test the blower motor to see if that is the problem? The car also has air conditioning which does not work. When the fan runs, it just blows regular air. There is an electrical plug that attaches to the freon line by the rad that has no power. I wonder if the plug is supposed to have power to it to make the conditioner work?? It has a small black wire that goes to the exhaust head, and it looks like a sensor. Then the rest of the wires go around under the alternator and over to another plug. Do you know what the problem might be?