Ok, since noone helped me in the 4.6 forum ill post it here.
(Ok i sort of know whats wrong)

Ok so heres the deal, i had a dead battery, i replaced it and eveything was good, checked all the fuses for battery drain and all that, but recently i was like...hmmmm....my heat guage is a tad bit more up than it is supposto, so i brought it home and looked, i realise nomatter how hot it is, moving or not, the radiator fan is not running *gasp* whats wrong X3......oh...and the low coolant light thing stays on, yes it is full and i double and triple checked, all the cables are plugged in...the light just stays on. Help me oh knowledgable mustang gurus

It only overheats when its sitting still, but what would cause the light and the fan to both trigger?

 

So from the way you described it the overheating problem started after you changed the battery?

If so then possibly when you were doing you battery drain testing thingy you didnt get the fan fuse back in good.

The reason its getting hot only when sitting still is because the fan isnt coming on. When you drive enough air flows in to keep it cool enough.

It may be that the low coolant switch uses that same power.

 

GOoooood question...but i pulled all the fuses and checked them, i dont know which fuse is the fan one :\

 

Then it looks like you have to go back and recheck them all again. Make sure power is actually getting through them. Sometimes a fuse will look good, and be blown. A simple way to check if your fan comes on or not is to kick on your AC. On these cars the minute you click on the AC the fan starts and runs until you turn it off.