could be a few things. there is a motor that drives the temperature control, which opens/closes a valve to the heater core. and also down under the steering wheel, to the left, on the removeable panel is a small vent with a pipe from the AC. check to make sure thats operational. i believe there is a sensor in there.
also make sure the dash sensor for sunlight is plugged in and/or operational
i have spares of them all, if required