the controls inside are kind of simple if no one has mess with them , the vents or damper doors are controlled by vacuum from the engine , the A/C is turned on though a micro switch when you put it on A/C , your model have a thermostat on top of the case that cycles the A/C when it get below 34 degrees so it will not ice up, the wire goes to the compressor clutch , from memory i thing it was a black wire with yellow or white dash marks , if you turn the fan on with the engine running and and the contorls on A/C it should blow thought the vents ,if it does its ok , but if it blow though the defrost vent the vacuum is not hooked up , on the firewall you will see a rubber plug with to rubber lines out , the large one goes to a vacuum can them to the engine , the small one goes to the water heater valve , note , some years had two small hoses to the valve , hope this helps