An F150's alternator is responsible not only for recharging the truck's battery after the engine has started, but also for providing the electricity required by the engine and the truck's other electrical components. A discharged battery can therefore be caused by either a battery which no longer holds a charge, or by a defective alternator. Fortunately, changing the alternator on a 2006 F150 is fairly simple and usually takes less than an hour.
Remove both battery cables from the truck's battery using a wrench.
Locate the alternator on the passenger's side of the front of the engine, just below a plastic air intake hose.
Remove the air intake hose by loosening the clamp on each end of the hose with a screwdriver and lifting the hose off of the engine.
Remove the belt which surrounds the pulley on the front of the alternator. A single spring-loaded belt tensioner pulley is located underneath the alternator. Attach a 3/8-inch socket wrench to the square fitting in the center of the tensioner, then use the wrench to twist the tensioner downwards towards the driver's side of the engine and pull the belt off of the alternator's pulley. Note that a socket is not used here. The square fitting on the tensioner is deigned to accommodate the square mounting peg on the socket wrench.
Unbolt the alternator from the engine. Three bolts hold the alternator in place. A single bolt is located behind the alternator, and enters the engine vertically. The remaining two bolts are located at the bottom of the alternator. Remove all three bolts with a wrench and pull the alternator off of the engine.
Disconnect the alternator's wiring. Unplug the single wiring harness from the back of the alternator. A large wire with a metal loop on the end of the wire attaches to a threaded pole on the back of the alternator. Remove the nut which secures this wire to the alternator and pull the wire off of the alternator.
Plug the wiring harness into the fitting on the back of the replacement alternator. Slide the metal loop of the remaining alternator wire onto the threaded rod and tighten the nut onto the rod with a wrench.
Position the alternator onto the engine and install each of the alternator's three mounting bolts using a wrench.
Lower the spring-loaded belt tensioner pulley with the socket wrench, then position the engine's belt onto the alternator's pulley and remove the socket wrench.
Position the air intake hose onto the top of the engine, then tighten the clamps on each end of the hose using a screwdriver.
Attach the battery cables to the battery using a wrench.
