Replacing an alternator on a 2003 Ford Focus SE is a job rife with potential for frustration due to the location of the alternator. Unfortunately, since the alternator supplies all the electrical power for the Focus, ignoring a bad alternator is impossible. Once it fails, you must replace it before driving the Focus again. Anyone with basic automotive repair skills can replace the alternator in an hour or so with the right tools.
Loosen the lug nuts on the right front wheel with the lug wrench. Roll the floor jack under the right front and lift the Focus. Place the jack stand under the right front frame, not the suspension, and lower the Focus onto the jack stand. Pull the floor jack out when done.
Take the lug nuts and wheel off the right front by hand and set these off to the side, out of the way.
Open the bonnet and disconnect the negative battery cable using the battery cable wrench. Move the cable end away from the battery to prevent accidental contact while you are working on the Focus.
Plug the end of the belt tensioner tool into the serpentine belt tensioner, which is located on the front of the engine. Move the tensioner off the belt, by prying to the side with the tensioner tool, and then slide the belt off the tensioner pulley with your other hand before allowing the tensioner to move back into position.
Move to the side and access the front of the engine through the right front wheel well. Move the serpentine belt off the alternator pulley by hand.
Disconnect the wiring harness from the alternator by hand. Remove the ground strap from the alternator with the socket set.
Remove the alternator mounting bolts using the socket set. Pull the alternator out of the Focus through the open wheel well. You may need to turn the alternator more than once during this step to clear the suspension, depending on type of engine in your Focus.
Compare the old alternator to the new one, to make sure they are physically identical and then insert the new alternator into the Focus in reverse of how you removed the old one.
Reconnect the wiring harness by hand and the ground strap with the socket set. Slide the serpentine belt over the new alternator pulley by hand as well.
Move back to the top and pry the tensioner off to the side once again, slip the serpentine belt over the tensioner pulley with your free hand and then let the tensioner slowly move back into its normal position. Remove the tensioner tool when done.
Reconnect the negative battery cable using the wrench. Reinstall the wheel and lug nuts by hand. Lower the Focus off the jack stand using the floor jack. Tighten the lug nuts to 85ft/lbs with the torque wrench and close the bonnet.