Chrysler Repair: car overheating?, gauge reading, temp gauge

Question
My 2004 chrysler 300M overheated. The gauge in the the car was at mid level, slowly rose up then dropped done again only to go back up again. I turned on the heater in the car to highest setting and floor level, the gauge went down and then went back up again once I turned it off. Also, the air was hot at first then went to cold on heater setting. what is going can you help me? Is it the thermostat?

Answer
Hi John,
The gauge cycling up and down is normal and reflects the function of the thermostat. But is could be opening at a bit too high a temperature setting than it is designed to do.  The issue is does the gauge go to H or not, and are you seeing any steam coming out of the coolant overflow bottle or not? Another possibility is that there is air trapped in the system which needs to be bled away, but that would only likely be the case if the system had been recently drained and not refilled properly using a special refill funnel available at a dealer parts counter. So let me know what is actually happening with the temp gauge reading and whether there is any other signs of overheating. Also any relevant history about the system. Do you hear any bubbling sounds in the system or engine within a few minutes of starting the car? Please also identify which size engine that you have (2.7 or 3.5L).
Roland