If the alternator in your 2002 Toyota Sienna van is not properly functioning, it will cause the battery to drain very quickly. Because of its large engine compartment, the Sienna's alternator is simpler to remove compared to smaller vehicles. You should remove the current alternator before acquiring the replacement to make sure you get an exact duplicate alternator and so the shop can transfer the old alternator's pulley if needed.
Disconnect the battery's negative cable.
Unplug the electrical connectors to the alternator.
Loosen the alternator pivot bolt--located to the left of the drive belt--with a wrench, then loosen the lock bolt ,which is the lower of the two bolts to the right of the belt. Turn the adjustment bolt--the upper bolt on the right--counterclockwise to loosen the belt and remove the belt.
Remove the pivot and adjustment bolts and then remove the alternator.
Install the replacement alternator on the engine bracket and apply the bolts without tightening them.
Slip the alternator drive belt back onto its pulleys--this is also the belt for the air conditioner compressor--and tighten the pivot, lock and adjustment bolts.
Connect the electrical connectors to the alternator and then reconnect the battery cable.
Push down on the drive belt to test its tension--it needs to deflect by 1/4 inch if there is a distance of 7 to 11 inches between the pulleys and 1/2 inch if the pulley distance is 12 to 16 inches.
