Chrysler: cooling fan, Cooling fan

Question
I noticed that the cooling fan for the radiator does not come on when the engine gets warm. I turned on the AC and the fans kick on. What should I check. Could this be the temp sensor and if so where is it located? What else should I look for or check?

Answer
Please let me know the followings :
Your car name , model , year
If the temperature gage in your cluster indicates the temperature degree when the engine comes hot or not
Did you made any repair works or maintenance or wash your engine befor this problem appers or not
Your answers will help to fix the matter
Thank you,,,