I have an older model Night & Day brand Central Air Conditioner unit. The compressor is outside and the blower in inside. When I plug it in (the electrical outlet is in the closet with the blower unit) the fan will immediately come on. This unit is also the gas heater for winter. I can adjust the thermostat on the wall, turn it to cool and it works fine, it cools and it works, the problem is, when the temperature reaches where I set the thermostat, the unit will not turn off automatically, it will constantly run. I have to turn the thermastat on the wall to off that will shut off the fan/compressor outside and then go unplug the unit in the closet to turn off the fan/blower that's in the house. So, basically it is either off or on manually. Same thing when I use the heater, I can manually turn off or on the blower by unplugging it. Something isn't telling the unit to turn off or on. Could this be a thermostat or a sensor? Everything else is working fine, it just isn't "automatic" anymore.

Any ideas?

Thanks

Thermostat or relay in the inside unit