Suggestion:
Prior to the Alternator, take note and try this:
It takes approximately 9.5 volts to start a car. If you hear a clicking sound, your battery is not putting out enough voltage. Your radio, headlights, etc., will all work, so you will think that your problem is your starter. NOT SO. Either you have a weak battery which need charging, or the most likely culprit are your battery cables. Most people will look at their cables and if they LOOK clean, and don't see any white corrosion build up on the terminals, they believe the battery terminals are making a good contact. Once again – NOT SO. Those terminals and cables are lead. Lead is a shiny metal. Scrap the top of a battery terminal and it will shine. That darkness on the terminal you scraped off is also present between you battery terminal and cable, and will prevent a good contact. All it needs is to cause a drop in voltage to your starter and you will hear a clicking sound from the starter.
Get a good battery terminal and cable cleaner at your auto parts store. The type with the wires inside that will really make those terminals and cables shine. Once you have cleaned them, your battery will put out max voltage. If you still hear the clicking sound, take your battery to an auto parts store and they will check it. It may not be holding a charge or you may have a dead cell. However, DO NOT try and clean your battery terminals with Baking Soda or Coca Cola. I've worked on cars for over 50 years and all that does is clean the OUTSIDE of the terminals – NOT the connection between the cable and terminal.
So many people run out and buy a new starter or battery when it is really the connection itself.
Now the Alternator, with some info. you may use in the future.
The electrical system in an automobile is said to be a 12 volt system, but this is slightly misleading. The charging system in most cars will generally produce a voltage between 13.5 and 14.4 volts while the engine is running. It has to generate more voltage than the battery's rated voltage to overcome the internal resistance of the battery. This may seem strange, but the current needed to recharge the battery would not flow at all if the charging system's output voltage was the same as the battery voltage. A greater difference of potential (voltage) between the battery's voltage and the alternator's output voltage will provide a faster charging rate.
As long as the engine is running, all of the power for the accessories is delivered by the alternator. The battery is actually a load on the charging system. The only time that the battery would supply power with the engine running is when the current capacity of the alternator is exceeded or when engine is at a very low idle
Some people tell you that you can check your alternator by disconnecting it from the battery to see if the alternator can produce enough current to keep the engine running. Disconnecting the battery will subject the voltage regulator (and computer and audio equipment…) to significant voltage spikes which may cause an otherwise good alternator to fail. Even if there were no damaging spikes, this test would not indicate whether or not the alternator was good because the engine will easily run with a weak or failing alternator.
Simple Test:
If you want to see if your alternator is producing current, turn on your headlights when you're parked and the engine idling with the headlights shining on a wall (at night). Notice how bright they are. Then turn the engine off. The lights should get dimmer when you turn the engine off. If the lights get brighter when you kill the engine, the alternator was not charging sufficiently. When doing this test, the lights should be the only load (turn the stereo, a/c and other accessories off). With a heavy load, an otherwise good alternator may not be able to produce sufficient amounts of current at idle.
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