I am replacing the alternator on my 2003 ranger.
How do I release the tension on the serpentne belt to get the new alternator into place?

 

On the radiator support will be a sticker that shows the belt position for your engine and will also show the tension pully. You can try with a standard wrench but help you if it should slip off. The best is to borrow from parts store belt tensioner wrench kit. The tensioner will turn in the direction in which it will releave the pressure IE 3.0L in 2002 rotates counter clockwise (i think???)

 

I think all you have to do is put a wrench on the square part of the tensioner and pull it counter clockwise till the belt becomes loose then remove the belt. Thenease off the tension on the pully till you can remove the wrench. When your done ,reverse the order to put the belt back on.