What is causing the battery light to be lit in the dashboard and is my car blowing cold air when it hasn't done that before.

Two different problems. Unrelated. first, Ford used some sort of heater core by-pass in the 2000, maybe 1999 Taurus, a system that must not have worked very well because the went back after only a year or 2 to the vacuum operated valve on the inlet. Your heater core is either not getting fed with hot coolant, or is plugged. But the fix is to eliminate the bypass and allow water to pass through the core at all times, or have your car end up looking like this below... and/or install a manual shut off that you can turn off in summer. Now, the battery symbol is the warning of a failing alternator, or for whatever reason your battery is not accepting a charge if the alternator is good. Maybe bad battery, (if it's 5-6 years old, that's about the life span of a battery) or simply corrosion on cable terminals. click for full screen, this is what one guy did ...but either he got carried away or was doing something else.

I am not good at drawing with a mouse, but in the blue circle is the in/out for heater core, and the red is **I think** part of the squirrel cage blower and diverter, for defrost, floor, etc. This guy HAD to have some other project in progress. will go full screen

The big problem solved: The Alternator Connector eventually roasts and lands the wires. Disconnect and replace with a new one. The Duralast part number is 244. I replaced 2 Alternators and 1 Battery with no result. I finally found this. possibly all the Alternafores were fine