If you own a car, you have a fair idea of what starters and alternators are. Suppose your automobile is working fine one day but simply stops responding the next day, what would you make of it? The starter probably has developed a problem, but you think it could also be the alternator.Even if your car is starting and does not have a starter problem, it can shut off if the alternator is not working and charging the batteries while the car runs. The longer you run battery-dependent appliances in the car when the alternator is down, the faster the car wills shut down.The role of starters and alternatorsThese are two distinct components of a car engine. The engine goes from stationary to moving because of the starter. However, it is the alternator that provides the engine with power to keep it moving. Thus, starters and alternators together form an assembly that helps kick-start your automobile into motion. However, though their functions may seem similar, it is not as easy to figure out which one is causing problems, when it comes to an automobile not responding, as discussed above.How to differentiate between starters and alternatorsA bad starter or malfunctioning starters may not let the engine crank and start at all, while poorly performing alternators give themselves away when the engine is cranking, but devices using power, such as lamps or other electricity-driven functions such as a music system or power locks do not work. Another thing to remember is that alternators also charge batteries. Thus if your batteries are not working, it could be an indication of a poorly-performing alternator as well. How does the alternator charge the car battery? It does so by taking the energy of the running engine and converting it into electricity that is then used for recharging the battery as well as for supplying power to devices that need it.In contrast, when an engine is cranked, the starter uses electricity from the battery to engage the gears and eventually start the engine to put it into motion.For this reason, one way to differentiate between trouble caused by starters and alternators is to keep a close watch when you start your engine. If your engine starts with a jump-start (or someone pushing the vehicle to start), the engine is probably running fine. However, if the headlights are unusually dim or devices using electricity are not working, it could be an alternator issue.Heavy duty starters and alternatorsBoth starters and alternators have a shelf life, like other parts of course. However, the thing to remember is that these are typically ‘heavy duty’ pieces of equipment. Typically, if you discover there is mechanical trouble in your car due to starters and alternators, and you are advised to change either of them, you should stress on high quality, heavy duty spares.Keep in mind that starters and alternators, like other engine parts and spare parts are different for automobiles, depending on purpose and utility value. Even if the alternator works on a simple principle of harnessing electromagnetic energy, it needs to be heavy-duty. Ideally, you should source spares from a trusted agency, and one that caters to your brand of automobile. Not only does this ensure better performance, it also means your part is maintained well and lasts longer.