a series of guide of Alternator
2010-02-14

What Is an Alternator?

An automotive charging system is made up of three major components: the battery, the voltage regulator and an alternator. The alternator works with the battery to generate power for the electrical components of a vehicle, like the interior and exterior lights, and the instrument panel. An alternator gets its name from the term alternating current. Alternators are typically found near the front of the engine and are driven by the crankshaft, which converts the pistons' up-and-down movement into circular movement. 

Alternator is one of the indispensable auto performance parts with which engine cannot work without. For it is where the powertrain primarily derives power. In a simple electrical device such as flashlight, the power is directly taken from the dry cells to the bulb by the use of a circuit. However, a more complex and energy consuming flat iron needs to connect to unto a higher energy source which we call the alternating current in order to function perfectly. In the engineering of automobiles, alternating current cannot directly provide power, thus batteries are made available. In spite of the capability of the battery to run the machine, its capacity cannot last long travels. In this case alternators or alternating current generator should be used.

 Converting the mechanical energy into alternating current is what an alternator created for. The conversion takes place as the belt of the engine drives the shaft of the alternator. In this process the electricity is produced from the machine’s mechanical energy. After which, through diodes the power is being channeled. By then the electricity is used to recharge the battery or batteries as well as power the vehicle’s electrical system.

How do alternators work? 

 An alternator is the device that converts the power from the gasoline engine of a car to electric energy. It helps keep the battery of a car in good working condition. Some of the parts that make up a standard alternator are the rotor, the stator, diode trio etc.  

An alternator rotor which an alternator pulley drives is strapped around a core made of iron. Around this rotor are three coils which collectively make up a stator. The rotor rotation produces alternating current. The three diodes known as the diode trio supplies the alternator with field current. The battery also provides the alternator with field current. If an alternator is collapsing then at first no changes will be observed. Later however the alternator warning light will light up as a warning.

what happens when an alternator goes bad?

at first, nothing. That is because the battery has some reserve power in it, enough to keep the engine running for quite some time, many many miles in fact. So a bad alternator doesn't necessarily mean a tow truck should be called right away. As long as energy is conserved elsewhere, like turning off the blower motor, the rear window de-fogger, the stereo and the headlights (if possible), you could make it for some distance on just the battery reserve alone.

 One major problem which will finally occur as the battery loses its charge is that there will not be sufficient voltage to keep the engine running well. Many years ago I was in California and saw a car coming down the street with its catalytic converter glowing white hot and flames coming from beneath the car. What had happened is the alternator quit, the battery ran down, the engine was not firing on all eight cylinders and the unburned fuel was being burned in the catalytic converter! It had been long overdue for the driver to call a tow truck!  

 Before we get started diagnosing alternator problems there is one thing I must mention. Alternators use an "exciter" voltage to get the alternator working when you start your car. Now get this! About 90% of the cars made today run that 12 volts through the "battery" or "alternator" bulb (AKA the idiot light). So you need to check to see if this bulb is not burned out. It should light when the key is turned on! If it doesn't then there is a very good chance that the alternator will not put out!! Replace the bulb before beginning the rest of the diagnosis.

 how do you know when your alternator is going bad? 

 Most of the time the alternator dies slowly. Each of the three sections of the alternator generates its voltage out of phase with the other two sections. Each of the three phases has its own windings in the alternator and each of the windings has its own pair of diodes. Each of these windings and/or diodes can fail, one set at a time. If this happens the alternator can still charge the battery, but only with a limited current, approximately 2/3 of its original capacity if one system fails. If two systems fail, then it puts out only 1/3 of its rated capacity. And all that means to you is that you can go a long time on a half alternator. Chances are if you don't need headlights or air conditioning or other high current accessories, you would never know that the alternator was dieing!

what are you going to ask the mechanic when he tells you that you need a new alternator?

1. Did you perform a load test on the alternator? If you did, what were the voltage readings? Were they all below specification?? (mechanics will use a load testing machine instead of turning on all the accessories.)

 2. Did you check to see if the belts were old and cracked or possibly slipping?

 3. Did you measure the voltage at the alternator connector or at the battery? Were the readings the same at both places or is there a voltage drop somewhere in the system. You can tell him the "Dead Battery" story if you want to.

4. Finally, did you check the price on a rebuilt as well as a new alternator? (rebuilt alternators are just as good as new if they are done correctly and usually cost about 1/3 as much)

How to replace an alternator£¿

 Step 1: Disconnect the battery negative. This is an especially important first step, as all the electricity for the entire vehicle goes through the alternator. A wrench or a screwdriver across connectors can quickly fry voltage regulators, expensive engine computers, and cause injury.                                  

Step 2: On a v-belt vehicle there are usually two bolts holding an alternator to its mounts. One bolt or assembly maintains tension on the belts, and the other holds the alternator in place. First loosen and remove the tension bolt or assembly.                                  

Step 3: Next, loosen the pivot bolt.                                  

Step 4: Remove the pivot bolt. Remove electrical connections and slide the pivot bolt through the mount. Remove the alternator. This is a good time to check and replace worn belts.                                  

Step 5: Compare the old and new alternators to make sure everything is the same. Transfer any connectors or bolts from the old to the new.                                 

Step 6: Reverse the removal procedure and install the new alternator.                                

Step 7: Check belt tension. A little under an inch of deflection is ideal. Too much tension will quickly destroy bearings. Better a slightly loose belt than one too tight.                                                  

Step 8: On this vehicle, the alternator and the engine-driven accessories rely on one serpentine belt. A spring-loaded tensioner holds the belt in place. Slack allows the belt and the alternator to be removed.                              

Step 9: Start the vehicle and check alternator output with a multimeter.                               

Step 10: Re-check belt tension after about 500 miles. Adjust tension if required.