More than likely this is caused by a condition called "parasitic draw" on the battery. Meaning that even though the key is turned off, and removed from the ignition, something is still siphoning power from the battery. Any number of things can be the culprit. You will need to have a qualified service center do some troubleshooting to determine the source.
Under the battery, all the way down under the car. You'll have to remove the plastic curtain to access it.
It's attached to the throttle body.
The temperature sending unit on the 1999 Ford Taurus v6 is on the rear of the engine. It is closer to the driver side about 7 inches down.
On a 2001 Ford Taurus : ( No ) it doesn't have FAIL - SAFE COOLING like some of the newer Ford vehicles may have
Disconnect cablesremove hold down bracketLift out battery
You can view the 2005 Ford Taurus owners manual on-line at : www . motorcraft service . com ( no spaces ) Click on Owner Guides ( page 89 ) has the instructions with pictures
drivers side look at the top radiator hose that runs down between battery and engine. where the hose connects to engine you have to remove that housing and its inside. factory is 198 Fahrenheit
Bad connections somewhere in the car battery, alternator, feed line to ignition switch You must have a error code posted or the electrical is shutting down so the computer cant record an error.
The power window fuse (10amp, metric size) for a 2003 Ford Taurus is located in the #26 slot (far-right side, 4th down in regular fuse section).
The fuel pump relay on a 1999 Taurus is in the fuse box under the hood. It is in the second row down, the last relay to the right.
idle speed controll or tps throttle sensor
running lean. too many possibilities to narrow down