Carrier Weathermaker 8000 AC not stopping
The outdoor unit's contactor is welded shut, most likely

My first port of call at this point would be to check the contactor in the outdoor unit that turns power to the compressor on and off based on the Y signal from the thermostat -- if the contacts on that are welded shut, then the air conditioner will run constantly no matter what the thermostat and control board have to say on the matter.