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You Overheat and then you don't

Hi everyone! I have a possibly strange situation I need some help understanding. I drive a 2002 Honda Civic EX with about 105,000 glorious miles on it. I decided to hit the road and made a weekend road trip to pick up a stranded family member. I live in Ohio and drove Lou Dobbs, my car, to Florida. It was about 950 miles one way. All was well until I got to Florida. I hit my first traffic jam and was sitting with the windows down enjoying the Florida air. Suddenly, the temperature gauge started to climb! It got pretty close to the red but traffic began to flow at that point. As soon as I reached 40-50MPH the temp began to fall again. I picked up my cargo and headed back. Each time I would hit traffic or a red light the temp would climb without hesitation. This is without the A/C running. After I got back to Ohio, i asked a friend who knows about cars. Over the phone, he had me remove the radiator cap and reservoir cap to take a look at the fluid levels. After this though, the car has never overheated! I don’t understand. Can air get into the system and I let it out by removing the caps? I can sit in rush hour traffic for a half an hour with the AC running and the needle stays right in the middle. Should I still take it in to be looked at?

Thanks!

With the A/C on the radiator cooling fans should run all of the time. With the A/C off the fan will only cycle on and off based on engine coolant temperature.

From the sound of things it sounds like a radiator fan sensor has failed but an inoperative fan can also be caused by a blown fuse, failed relay, etc.
Checking this problem out should not be difficult at all.

OK is 100% right, with the AC on your fans are running and they should run with the AC off as well. I do not belive that is the case with your car at this point in time. It is most likley a bad sensor as OK says.