2006 Dodge Stratus COOLING SYSTEM

Hello. My car began to overheat 11 days ago. When it overheated I got it home. My father paid his cousin to work on my car. My father's cousin claimed my water pump and timing belt needed replaced saying the water pump was leaking and it made sense to do the timing belt at the same time. Five days later I get my car back. I drove it for less than an hour before it overheated again to boiling point. I pulled over and called my Dad's cousin. We noticed the antifreeze appeared to be gone so we refilled it and drove it home. He insisted that the thermostat needed replaced. I bought that and my finance installed that. I took it to work. Within 2 hours it overheated again. This time it was taken to a transmission specialist auto shop. This mechanic said he felt the radiator was bad because of rust and debri in my overflow tank. He said my car passed his "compression" and pressure test. He Replaced the radiator today and gave me the car back. When I got into my car within the first 5 minutes I noticed the original antifreeze smell I used to smell was gone. I noticed the temp gage was higher than normal. It usually sits at about the 30% mark and it was about halfway 50% but the mechanic said that can be normal not to worry. So I drove off. I decide to take it for a test run from Essex to Highland town. About 3 miles from the shop I decided to turn on the A/C. Then about 4 miles later I saw the temp gage move a hair above the half way mark, so I decided to drive it a little further. About 3 more miles and the temp gage was about 3/4 high. So, I turned the heat on. The temp gage dropped very fast back to the halfway mark. When the A/C is running for 30-40 minutes my car will overheat. I do not know why. My mechanic said my fans are working properly. I noticed when they A/C is on they do not constantly stay running, they cycle. My mechanic said that is normal. My coolant level did not go down I noticed. I did think that the coolant looked kind of clear. I was thinking the mechanic may have used more water than he should have as opposed to the coolant. Can you help me diagnose this problem?