If the battery in your Nissan Pathfinder is losing power quickly, the alternator may be the problem. The alternator uses the motor's own energy to recharge the battery. In many trucks and other large vehicles, changing the alternator can be a simple procedure, as there are few other components in the way of removing it. You must still, however, use caution, as you are dealing with the voltage of the truck's electrical system. As is the case with any vehicle, the replacement alternator must be identical.
Loosen the cable clamp nut for the truck's negative battery cable and remove the cable from the terminal. Set the cable aside where it can't accidentally contact the terminal.
Raise the truck and support it on jack stands. Unbolt and remove the side and lower splash shields if your Pathfinder is equipped with them.
Disconnect the output wire from the alternator; the wire has a sphere-like connector. Disconnect the rectangular-shaped electrical connector, which is right next to the output wire. Unscrew the ground wire with a screwdriver and remove it.
Remove the drive belt from the engine, loosening the bolt in the center of the idler pulley with the wrench and slipping the belt off the pulleys.
Remove the two mounting bolts for the alternator and remove it from the engine.
Install the replacement alternator and apply its mounting bolts.
Connect the ground wire, electrical connector and output wire to the alternator.
Reinstall the drive belt, making sure it is routed along the pulleys in the same path as before. The belt does not need to be tightened yet.
Reinstall the splash shields with their fasteners and lower the truck off the jack stands.
Reconnect the battery cable.
Tighten the alternator drive belt using the wrench on the idler pulley bolt. The belt should not give more than a quarter-inch when you press down on it in the center with your thumb.
