2003 Chevy Blazer Temp gauge

Engine Cooling problem
2003 Chevy Blazer 6 cyl Two Wheel Drive Automatic

Please help diagnose the following problem:
My temp gauge and my oil gauge are not working properly. My terminology will be horrible so bare with me. My temp gauge will not stay at the half way point. It is suddenly sitting at the 3/4 point. I know it's not low on fluid because the over flow has antifreeze plus I've checked. My oil gauge goes from 1/4 point and bounces-never idle for any time.
*I live in Phoenix, AZ
I turned my air on two weeks ago and that is when I thought I blew my radiator. My temp gauge jumped and when I got home It appeared to be leaking. Not so! It wasn't antifreeze leaking! I bought Bar's Stop Leak and now my gauge sits @ 3/4. I have no explanation for the oil gauge. That has been going for a year now. My main concern is overheating.