Hello, I have central heat and air installed in my house. Recently, when the air conditioner shuts off automatically, the fan continues to blow. I've tried turning the air off heat switch to off and the fan switch to auto, but it still runs. I'm not sure what to do and I am concerned that at the end of the month I will be receiving a huge electric bill. I also have general question about the air conditioner fan. Exactly what is it for and what is the purpose of having it switched to automatic. You have to forgive me, but I am not very appliance oriented. Please advise. Thank you.

The fan may continue running due to a bad blower relay, the purpose of the ON/AUTO switch is so that you have the option to run the furnace fan continuos or cycle with the heat or air conditioning. I wouldn't worry too much about this problem, it won't run your bill up very much, but it should be looked at asap for this could mean something is shorted or worn out inside the furnace. If you would like, we can try to walk you through some steps to figure this thing out, but if your not very handy, my best advise is to call in a pro. if this system is fairly new it may also still be under warranty.