Maybe the problem isnt the tensioner...
Is the belt really loose? It might be a siezed up alternator, power
steering pump, water pump or A/C compressor pulley.
But the tensioner pulley and tensioning device are not too hard to
find.
If you look closely, you might see that the belt goes AROUND those
items I just mentioned, but the belt kindof goes BEHIND the tensioneer.

To remove it you'll need a socket wrench (14mm, I think) with a very
long handle just to take all the tension off the belt.
Once the belt is loose, slip it off the alternator. Then without the
belt, you can check to see if all the pulleys are "rotate-able".
To get the tensioner assembly off, simply unbolt it. It's attached by
a short arm to the tensioner pulley.
I dont know which parts of the tensioner are replaceable. You may or
may not have to replace the whole thing.
-WaV

tonya wrote:
> Hi wondering if anyone can help. My serpentine belt was squeeling and
> now is so loose the car won't start. My battery and ABS lights came on
> the day before. How do you change the belt tensioner? And where the
> heck is it located.. I looked in the Haynes manual but it isn't very
> clear. Thanks