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It's good to know what makes up an alternator, that way you can be prepared for the automotive language used by your parts professional.
The housing of the alternator is usually made of aluminum. The housing is made with bolt holes, so the alternator can be attached to the vehicle. The internal parts are made up of a iron core called the strator. This core is surrounded by thousands of copper wires that are electrified by a rotor spinning inside these copper wires. This creates a magnetic field and AC current. Since vehicles need a DC current, there needs to be a part that converts AC to DC. That part is called a diode pack and it allows the current to flow in one direction. From there, the current is sent to a voltage regulator, which regulates how much voltage is sent to the battery. This is where the power comes from to keep our battery charged.
Remember, the voltage regulator can fail and getting too much voltage to your battery will cause the battery to fail, too. The proper amount of voltage for a battery is about 13.5 volts to 14.5 volts, exceeding this voltage or decreasing this amount of voltage will cause alternator failure and the battery will fail.
The alternator is part of the charging system on a vehicle. In many cases, it is easy enough to remove and replace the alternator, but on some vehicles, you may not be able to access the bolts without removing other parts. If you need to do this, be sure you have the instructions to remove the parts that are in the way. Label wires and hoses so you know where to put them when you put everything together.
Also, before you start, locate the belt diagram. If your vehicle’s belt diagram sticker is missing from the hood or radiator shroud, sketch the belt’s routing before you take it off, especially if your vehicle uses a serpentine belt that is routed around all of the pulleys.
Before you put your hands into the engine compartment, remove the positive battery cable. It is always a good idea to tag the wires going to the back of the alternator. If you attach the wires in the wrong place, you could fry the alternator and the store and manufacturer won’t cover that mistake under warranty.
Remove the serpentine belts or V-belts. If your vehicle has V-belts, remove only the belts needed. Usually V-belts use a slider to put the proper tension on the belt. Simply loosen the slider bolt, push the alternator toward the center of the engine and lift the belt off the pulley. You do not need to remove the belt from the other pulleys.
If your vehicle has a serpentine belt, rotate the belt tensioner toward the center of the engine. This will provide enough slack so that you can remove the belt from the alternator pulley. You can leave the belt on the rest of the pulleys if you don’t have to remove one of the other accessories.
Unplug the alternator wiring harness connector. Remove the nut holding the power wire onto the alternator. Set the wire aside, then put the nut back on the stud for now — just so you don’t lose it. Remove the alternator and set it aside. Don’t throw it away — most places charge you a core charge, which you get back when you bring it into the store.
Install the new alternator. Reinstall the belts. Reattach the alternator’s wiring -- get the nut for the stud from the old alternator. Reinstall any other parts you may have had to remove to complete the alternator replacement. Reinstall the belts. Tighten the belts. If you have V-belts, tighten the belts until you can twist the belt 90 degrees. If the belts won’t tighten, make sure you have them on the right pulleys. If they still won’t tighten, the belts need to be replaced because they stretched.
If you have a serpentine belt, install it around all of the pulleys except the tensioner. Rotate the tensioner toward the center of the engine and slide the belt over the tensioner. Make sure the marks on the tensioner are in the correct range. If they are not, replace the serpentine belt — it stretched so far that the tensioner won’t tighten it.
Reattach the battery positive cable. Start the vehicle and using a voltmeter, be sure the alternator is charging the battery. The battery must have at least 12 volts before you start the vehicle or it will look like the alternator is not charging. Furthermore, you could damage the alternator if you try to charge a completely dead battery by running the vehicle. Use a battery charger to charge the battery. If everything checks out, the alternator should be putting out between 13.5 and 14.5 volts when the vehicle is running.
Not many people will tackle a job like repairing an alternator, but some find it very cost effective to do so.
For those who would rather replace an alternator, here are a few tips that may change your mind. Consider the cost of a replacement or an upgraded alternator.
For a 2000 Chevy Silverado, a replacement can be up to $250. For an upgrade, double that. For repairing the same alternator, depending on the kit you want to purchase, the cost is between $30 and $70. For an upgrade, add anywhere from $5 to $70, depending on the upgrade, vehicle and its use.
Be aware of your vehicle's capabilities before attempting an alternator rebuild. Know your vehicle's intended use and do not go overboard with a rebuild. Don't exceed or decrease the amount of voltage or amps that is described by the alternator manufacturer.
There have been many, many suggestions when it comes to testing an alternator for the appropriate voltage or amperage.
Magnet Tests: Supposedly, if the back of the alternator housing is magnetized or if the alternator is going backwards, then the alternator is going bad.
The Alternator Can Fix Itself: If an auto part could fix itself, there would never be any reason for a mechanic.
A lot of myths are floating around about auto parts and how they can be fixed or tested, but in reality auto parts go bad, malfunction or fail. Just about any auto parts store and most dealerships test alternators, starters or other auto parts and will usually test them for free. These tests are done by computerized machines that are more effective than any other method. These are very accurate tests, and should be used whenever possible.
So you need an alternator, and you need to save money? You can get a rebuilt alternator and save some money without losing reliability. A bosch alternator, for instance, has an exellent warantee and is rebuilt with all of the most important components.
This way, you get a great car part without shelling out a ton of dough. If you go with a rebuilt alternator, make sure you go with a good brand name. Super cheap car parts are not the answer - the key is to get a good buy. Additionally, you can get these rebuilt alternators from reputable car parts providers so you have a way out if it does fail (which it won't!).
Like all aspects of your car, your electrical system can be exponentially upgraded. Perhaps you have a work truck for on site welding, generators, etc. or you have a crazy sound system that requires extra amps - you will need to upgrade your alternator.
So, a regular car alternator provides between 60-90 amps while a high powered alternator will support over 200 amps for after market accessories. Choose wisely - assess what you really need (in terms of power) and then shop around. An alternator upgrade tip: although you may think the alternator is the only thing you need to worry about when you upgrade your system, you also have to upgrade your wiring so it can hold the juice.
An alternator is the base of the charging system of your car. Not only is it integral to all of the electric systems of your car - the radio, the lights, the fan etc. - it also keeps your battery charged. When cars were first built, car manufacturers actually used small generators for their electical systems. Alternators offer more efficient power and they are also safer. When your car alternator fails, so does your car as your battery is completely depleted.
When your battery light goes on, it may be the battery, but 9 times out of 10 it has something to do with a failing alternator. For newer cars, a mechanic is almost always necessary for a swap, but that shouldn't stop you from buying your car parts yourself. By shopping around on car parts websites, you may be able to get the part for less money and just provide it for your mechanic.
Is your car having the following symptoms?
• Dim lights
• Hard starting
• Dead batteries
This may mean your alternator is on its way out! Here is how to troubleshoot:
1. Grab a simple multimeter, digital or otherwise
2. Check for loose connections to and from the battery, to an from the alternator etc.
3. Once you have established that the connections are secure, measure the battery voltage with your multimeter when the car is on and off (maintain all safety precautions).
4. Measure the voltage from the output of the alternator.
Chances are you are going to see a problem with the battery or with the alternator because issues with your electrical systems usually come from one of four things:
• Short Circuit
• Bad Voltage Regulator (in the classics)
In older cars, like your stock mopar for instance, your alternator was paired with a voltage regulator which prevented your alternator from over charging your system. Nowadays the voltage regulator is built into your car alternator, so you don't have to worry about wiring to and from the voltage regulator and alternator (as you will soon learn, fewer connections makes for easier troubleshooting!). If you have an older car, it is advisable to replace both of these parts with a newer version. Old voltage regulators can be tweaky, and it is really best to take them out of the loop if you can.
|Jennifer Mathes, Ph.D.|