How do you tighten the drive belt for 1996 Ford Taurus?

Answer 1

It has an automatic belt tensioner. If the belt is loose it means the tensioner has failed and needs to be replaced.

If you feel competent to try, belt tensioners are not difficult to replace. Purchase a new one (and a new belt, since you need to take the old one off anyway, it's cheap insurance). then locate the part on the front of th engine that resembles the part you just bought, and simply unbolt the old one and bolt on the new one.

Two caveats;

One, DO NOT disassemble the tensioner, there is a tightly coiled spring inside that can injure you quite badly.

Two, you may want to get a "Serpentine Belt Tool" to help with installing the new belt, this tool allows you to pivot the pulley on the tensioner so that the belt can be slipped over it. Most auto parts stores will rent you the tool for free.