location of temp sensor on 1999 Cadillac DeVille

engine fan will not come on only when i turn the heat or ac on. location of temp sensor

2 answers
The coolant sensor on the northstar engine in your 1999 Cadillac DeVille is located on the back end of the rear head. Not very easy to get to as I remember. The cooling fans should come on at about 230 degrees.
the engine is overheating and is throwing water out