Alternator problem signs and how to replace Alternator

Alternator problems and how to replace Alternator
Alternator problem signs and how to replace Alternator

What is the alternator and how the alternator works

The term alternator is a shorthand form for alternating current (AC) generator. An alternator produces alternating current (AC), which is internally converted to the direct current (DC) for use in the various accessories and car’s electrical systems.
when the engine is operating engine drives a belt that enables your car or truck alternator to produce electric current for the rest of the journey. this is the way how this system works: Your car alternator replaces the electricity that was taken from the battery when you started the car. Then, every time your battery spends some of its power, the alternator produces electricity to recharge the battery and to stabilize the voltage in the electrical system. If the alternator fails, the battery can supply power for the car until it becomes discharged.

Alternator problem signs


you can be a little hard to diagnose alternator problems without any tools.some times can be Battery problems seem like alternator problems. The alternator keeps the battery charged and provided current for the vehicle’s lights and other electrical accessories of the car. An alternator failure will allow the battery to run down, The first sign of alternator trouble could also be dim headlights or an engine that is slow to crank. the most common things that can happen are things like your car battery going dead, serpentine belt squealing and battery light on. These are the most common signs, but there are more others

When the alternator is generating an electric current, it’s said to be charging. if the alternator isn’t working properly, some vehicles have gauges to check called voltmeters that show whether the system is charging or discharging. they have a range of voltage levels usually from 8 to 18. some of the voltmeters have a “C” at one end and a “D” at the other end of the scale. when the engine is operating and all accessories off, the system voltage should be 13.5 to 14.5 volts If not, something may be wrong with your car charging system. also now most cars just have dashboard “idiot lights” that will go on.

How to Check Alternator


your old alternator needs to bench tested. Alternators have one of the highest warranty return rates among any vehicle components. because of faulty diagnosis, many units are returned needlessly (there is nothing wrong with the original unit or the replacement unit), One way to stop this problem is to take your alternator to an auto parts store with an alternator bench tester and have to test alternator before you buy a replacement. If the old alternator test failed, you need to replace the alternator. But if the test is good, the problem is something else in the charging system.

Disconnect your battery.

to prevent any shorts or grounds that might happen if you accidentally touch a battery positive wire at the alternator against anything metal. You need to disconnect the battery first. There is NO danger of being shocked by 12 volts, but the sudden voltage surge could damage sensitive electronics in your vehicle or the wiring. if you have a vehicle manufactured in 2004 or after, Don’t forget to connect a battery memory saver before disconnecting the battery

Remove the alternator drive belt.

in vehicles with a serpentine belt and automatic belt tensioner, locate the belt tensioner. have to use a socket and long handle to rotate the tensioner. the direction you want to turn the tensioner will depend on how it is mounted and how the belt is routed. On vehicles where the tensioner is located in a place hard to reach, you may need to use a special long handle serpentine belt tensioner tool, or have to do this from underneath the vehicle.

NOTE: look for an underhood decal that shows how the belt is routed Before you remove a serpentine belt. If you can’t find such a decal recommend you to, draw a picture of how the belt is routed, or simply take a photo from your phone so you can see it later when you put the belt back on. The routing of some belts can be very confusing to you, so before you take it off make sure you know the way how it is supposed to be routed.

If your car has a serpentine belt for the alternator but there is no automatic tensioner, follow the same removal procedure for a V-belt (to loosen the alternator pivot bolt and adjustment bolt, rotate the alternator inward to loosen the belt, after that remove the belt).


On vehicles that with a V-belt, loosen the alternator pivot bolt and the adjustment bolt on the alternator support bracket. Swing the alternator inward to relieve tension on the V-belt, after that slip the belt off of the pulley.

Disconnect the wiring from the alternator.

it may be easier for you to disconnect the wiring after the alternator bolts have been removed, for easier access you can turn or rotate the alternator.


But you don’t need to twist the wires too much and don’t let the alternator hang by its wires, it can easily damage the wiring connectors or terminals. That’s the reason why we recommend you to disconnect the wires before you remove the alternator.

NOTE: there are multiple wiring terminals or connectors on the back, of alternators. don’t forget to remember which wires attach to which connectors. if you install back the wires on the wrong terminals, it may be possible to prevent the alternator from functioning or possibly damaging it or damage to other electronics in your car.

Unbolt and remove the alternator

usually, Alternators have two or four mounting bolts.
two bolts are standard (a large pivot bolt and a smaller adjustment bolt on the alternator support bracket ), on the applications where the position of the alternator can be adjusted to tighten the belt.

On the applications where an automatic tensioner is used to maintain belt tension, usually, the alternator is rigidly mounted to the front cover or mounted to the engine with four bolts

buy a new alternator or a reconditioned alternator

before buying a new alternator or a reconditioned alternator( a tested one )
Make sure you are buying the correct unit for your vehicle, some alternators look like the same but they have different power ratings and different wiring connections.

Mount the replacing alternator on the engine

now Install back all the mounting bolts, but don’t tighten the bolts fully, if it must have to be rotated to tighten a V-belt or a serpentine belt that does not use an automatic tensioner.
Reconnect the wiring to the alternator

this may be easier to do before you mount the alternator on the engine if access to the back of the alternator is limited. make sure all of the connections are clean and tight, and all wires are routed correctly. with bad connections, the alternator will not work properly

replacing alternator
replacing alternator

Reinstall the belt

Slip the belt over the pulleys, make sure it is correctly aligned and routed correctly, then tighten the belt if no automatic adjuster is used.

This needs to done by carefully prying outward on the alternator housing until the belt is tight, then tightening the pivot and adjustment bolts. You may need a helper to do this

On applications with an automatic belt tensioner, you have to rotate the tensioner inward and hold it so the serpentine belt can be slipped over the last pulley

Reconnect the battery

Reconnect the battery
Reconnect the battery

now finally need to reconnect the battery, first, install the positive cable then install the ground cable. if the alternator and charging system is working correctly. You should see 13.5 to 14.5 volts after starting the engine and checking the charging output with a voltmeter.

Working with car batteries or on electrical system parts in the car can be dangerous.
Batteries contain sulfuric acid, a powerful corrosive. When batteries charge, batteries release hydrogen gas, which is explosive.
Metal tools and objects can conduct electricity and cause a short circuit or accidental ground that results in sparks and extreme heat.
Always perform your car battery or electrical system work in accordance with the instructions printed in your car manufacturer’s repair manual.


guide to safe practices when you work with batteries

  • always remember to wear safety glasses Battery explosions can splatter sulfuric acid into the eyes. and wear gloves, when working with your car or truck battery.
  • before you start work remove all watches, rings, neck or ankle chains, and other jewelry from your body.
    Metal items can conduct electricity and cause a short circuit, burns, sparks, and possible to make battery explosions.
  • Remember to Keep sparks, flames, and other ignition sources away from the car battery
    flames, Sparks, or smoking materials can ignite hydrogen gas produced by the car battery and cause an explosion.
  • as soon as you finished the job wash your hands and clothes

READ MORE How to replace a car Battery

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