Once upon a time, the lights, horn, and heat blower were the only parts of your vehicle that needed an alternator to function. Powering these electrical accessories took about 50 to 60 amps from your alternator and you most likely had some power left over. Nowadays, our cars and trucks are considered high-output vehicles that require much more juice. Modern amenities such as heated seats, HID headlights, high-amp stereos, and moon roofs work your Lexus alternator hard. That is why 100+ amp alternators are becoming more commonplace. Considering all the components your alternator needs to power, it should be no surprise that eventually you may need to replace it. The four most important parts of your alternator are: the rotor, stator, voltage regulator, and diode packs. Any of these parts can fail for a number of reasons and if even just one malfunctions, you will need a whole new alternator.