GM-GMC: 1999 GMC sierra 305 4x4 ext cab, blower motor resistor, fan selector

Question
can you  tell me why the  A/C would go out completely ( no blowing, no sound or lights) and the battery  light  will come on on the message center. Even though the  battery  charging  light is  fine  I  can run all the lights and radio and all electrical.

Answer
My initial thought is that you have two seperate concerns.  To look at why your blower motor isn't running.  To get access to the fan motor you will likely need to remove a cover on the passenger side under the dash.  Unplug the fan motor and with the key on and the fan selector on high, use a test light and test the connector for power and ground.  If you do have both, replace the fan.  If you don't, unplug the blower motor resistor located right next to the fan, actually where the plug for the fan itself comes from. Unplug the connector that enters it and inspect the terminals carefully, they will often corrode and melt.  If that is okay, you have two options.  You can get a new resistor and plug it in and see if the fan works or you can probe the connector for power and ground with the fan selector in different positions.  Unfortuneatly I don't have a wiring diagram handy to tell you what wire will have power at what setting.  Check that out and see if your charge light persists.
Hope this helps a little bit.