In a car, the alternator is the car part that powers the electrical system. In fact the alternator is a sort of generator that produces a small field voltage for your Toyota. The alternator works only if the engine of your Toyota is switched on. In addition to powering the electrical system, the alternator charges the car battery quite like a bicycle generator powers the lights when you're cycling. On a bicycle the generator produces enough electricity for the lights. Car lights are a lot more powerful though which is why your Toyota alternator needs a voltage regulator to transform the small field voltage into a constant current. An Toyota alternator costs between £100 and £300 depending on the model of your Toyota. We therefore ask you to enter the relevant model and engine into the search engine to determine which references are suitable for your Toyota."