[webo97]

What's the 3 slits in the dash just right of the steering column? ...

That would be the In-Vehicle Temperature Sensor. Here is the service book
description.


In-Vehicle Temperature Sensor

The in-vehicle temperature sensor contains a thermistor, which measures the in-vehicle air temperature and sends that reading to the HVAC module. An aspirator hose is connected between the heater core and evaporator core housing and the in-vehicle temperature sensor. The aspirator hose uses airflow through the heater core and evaporator core housing to create a Venturi-type suction to draw in vehicle air through the in-vehicle temperature sensor (across the thermistor).
The in-vehicle temperature sensor is mounted to the instrument panel to the right of the steering column.