Overview of Locating, Troubleshooting, and Installing Alternators

By: Dusty Arlia
Published on November 19, 2011
Last Updated on Tuesday, July 14, 2015 at 2:25 AM
Total Updates: 4

Modern cars get electrical power from the alternators. Alternators come in different shapes, but their function is the same - making alternating current (AC) that is then sent through a rectifier to convert it to direct current (DC) for the vehicle. Rectifiers are an important part of alternators. Alternators generate their power from circular motion. They create AC and use the rectifier to change the current to DC. Some of the reasons for needing to replace your alternator include having problems starting your car and issues with low voltage. Low voltage can be identified by have your lights dim or not being able to power accessories properly.

The first step in replacing your alternator is locating it under the hood of your car. When you open the hood on a vehicle you will see at least two things driven by a V-belt or serpentine belt system. Those things could be an alternator, power steering pump, air conditioning compressor or some kind of accessory like an air compressor or engine fan. Unlike the A/C compressor or power steering pump, alternators do not have any hoses or hard lines going to them either, just wires. Generally an alternator will have some sort of cooling fan on or in it and a case that has a lot of open vents for cooling. The alternator will normally be mounted near the top of the engine, but not always.

A/C compressors have an electric clutch at the front that activates the compressor. They never have cooling spaces.

Today, all vehicles will have an alternator and power steering, but A/C is still an option.

If you had a reliable alternator for years that finally needs replacing, than replacing it with an alternator with the same specifications should be fine. If you been having electrical issues than further investigation is needed.

When figuring out which alternator is right for your vehicle, figure out the necessary amperage you need. If your vehicle needs 75 amps to start, make sure you have at least an 80-amp alternator to make sure you have some margin of error.

Also, be sure to use a battery and alternator with the same amperage rating. If you had issues with lights flickering when you had an accessory turned on, it is a sign of low voltage. Solve this issue by recalculating your total amperage requirements by adding up the amperage requirements of each accessory - lights, sound system, video system, air conditioning, GPS navigation, power steering (very few are electric), heater and fans (if you have an electric cooling fan you need to add this too). The total amperage should not exceed the amperage of either the battery or alternator. If the amperage adds up to be greater than the battery or alternator, you need to upgrade both. High amperage alternators generally do not last as long as OEM (original equipment manufacturer) alternators because they produce far more heat. Also, two batteries are better than one high-amp alternator and costs less.

You can find aftermarket, stock, and custom built alternators for almost any vehicle. High-output, high-amperage alternators are also available. Most high-amperage alternators are built from the stock housing so they should fit just like the OEM unit you are replacing. Modifying the mounting on these units is rare, but sometimes necessary if the housing is different.

Also, on a rare occasion a second alternator may be found in certain specialty cars. They are either powered by a drive belt or drive a belt by connecting it to the driveshaft. In order to generate electricity on these vehicles you must be moving at a decent speed.

By comparison to today's alternators older vehicles used to use generators, which generated direct current. Alternators are used now, because they are more efficient, especially at low engine speeds.