What does the starter do?
To make an engine start it must be turned over or “cranked”, so that it can pull a mix of fuel and air into the cylinders, and compress it. The powerful electric starter motor
does this turning and kick-starts the engine and combustion process. The starter needs a heavy electric current, which it draws through thick wires from the battery. The switch must be turned on and off very quickly to avoid dangerous, damaging sparking. So a solenoid
is used - an arrangement where a small switch turns on an electromagnet which completes the circuit. When should I replace the starter?
The following are possible signs that your starter needs to be replaced: engine won't turn over, starter engages but doesn't spin the motor, grinding noise when trying to start the motor, or smelling or seeing smoke when starting the motor. Problems with the starter are virtually impossible to avoid, as there really isn't a replacement schedule recommended by the automotive manufacturer. As soon as you notice your vehicle’s freewheeling, grinding noises, smoke, or your vehicle does not start at all, contact a professional mechanic to further assist you in figuring out the problem.
What does an alternator do?
You know that your battery stores electricity, enough to start your engine and get you moving. Unfortunately, that's about it, as you can only get a few miles on battery power alone. You need an alternator
to generate enough electricity to run your engine and power your electrical accessories like the stereo, power seats, heater fan, on-board computers, and so on. On top of that, the alternator’s job is to recharge your battery. So when your alternator isn't working properly, there isn't enough electricity to power your electrical accessories; when your alternator fails, you aren't going very far… What are the signs of a failing alternator?
Usually, failed alternators have simply worn out. Alternators are driven by a belt and spin 2 to 3 times faster than the engine – that's hard work! The bearings wear out, as do the copper wire coils and magnets that generate the electricity. A few warning signs that your alternator may be starting to fail are: dim lights, warning light, weak or dead battery, weird smells, or odd sounds. There's no point in hobbling along with an alternator that's not working properly. It will fail and leave you stranded, so replace this failing alternator as soon as you can.