300E runs hot with A/C on....HELP!!!

[mike690003]

Hello Board,

I rarely use my A/C, but today I decided to use it(it was really hot). My temp is usually about 85-90 C . Well I turned on my ac and right as I got into havy traffic the temperature started to climb. I went all the way to about 110 C. Well I had my expansion tank and cap replaced and I also had the cooling system flushed. My cooland/water mixture is a perfect 50/50. I have no leaks, What could have caused my car's temp to run so hot???

Do I need a new thermostat??? If so, what kind? a colder or hotter one???

Help!!!