I have my AC fan set to AUTO but it won't ever turn off. I finally had to turn it off from the main fuse box because I was worried it might either burn out or worst. The AC/HEAT is set to OFF. Any ideas about what I should do to make sure it turns off?? Thanks.

Look for a defective relay in the furnace unit or a defective fan/limit control that has welded shut and keeps the fan running. It could also be thermostat wiring if you changed your thermostat lately.

First get a voltage meter, but make sure your t-stat is set to auto, take the door off the furnace while holding the safety switch in test the g terminal with one lead and common with the other, if you have 24 volts and the fan switch on the stat is on auto and system is off. Then it's the t-stat, if not you have a stuck blower relay