Chrysler Repair: temperature gauge, cyl engine, faily

Question
I just had a rebuilt motor put in but the temp gauge fluctuates while im driving back n fourth between 1/4 and 3/4. Sometimes jumps back n fourth faily fast. This moring it was 35 degrees outside and it went up to 3/4 fast stayed there for a while then went back n fourth again. Some days it runs normal like all day yesterday.What can i do?  

Answer
Hi Don,
This may be normal; it depends upon what year and engine you have in the car. It may be reflecting the normal thermostat opening and closing; but it also could be due to air trapped in the thermostat housing if you have a 4 cyl engine of the '80s and early 90's which require a special approach to cooling and refilling. So let me know about those model details and I can tell you how to get rid of the air if applicable. I would not be alarmed as long as it doesn't go full scale.
Roland