The Toyota Highlander has an alternator that sends electrical current to various devices in the vehicle while the engine is running. Most alternators made today include a voltage regulator that ensures the voltage level remains constant. You may need to replace the alternator if your battery keeps running down or your headlights become dimmer while driving.
Determine which alternator your Toyota Highlander will need. You'll want to be sure the new alternator is compatible with your Highlander's engine. Models made before 2008 may have a 2.4 L, 3.0 L or 3.3L engine. The current version has a 3.5 L 2GR-FE engine.
Disconnect the negative battery cable with a socket wrench. Remove the electrical connector and the retaining nut on the alternator terminal with a socket wrench. This will allow you to remove the battery terminal wire on the alternator.
Unfasten the pivot bolt and plate washer, and adjust the lock bolt from the alternator with a socket wrench. Remove the drive belt and take the alternator off the vehicle.
Install the new alternator assembly. Replace the drive belt and adjust the tension to 170 to 180 lbs. for a new belt and 95 to 135 lbs. for a used belt. Use a torque wrench to tighten the adjusting lock bolt to 13 foot pounds. Install the plate washer and torque the pivot bolt the 41 foot pounds for a 3.0 L engine and 43 foot pounds for a 3.3 L engine.
Connect the electrical harness and battery terminal wire to the alternator and fasten the retaining nut to the alternator terminal with a socket wrench. Reconnect the negative battery cable with a socket wrench.
