Corolla Alternator Problems: Symptoms & Diagnosis

A bad alternator can leave your Toyota Corolla without power and unable to move. Alternators do not always fail in the same way. Here we will tell you all about the Corolla alternator problemsso read on.

We’ll also teach you how to detect the symptoms of a bad alternator, and how to diagnose a bad one (which is a very easy task).

How does your Corolla’s alternator work?

Corolla Alternator Problems
Toyota Corolla 2008

The job of the alternator in your Corolla is to provide electricity while it is running. The battery stores enough voltage to be able to start the engine without the help of an alternator.

It is rotated by a serpentine belt. It’s worth noting that a bad serpentine belt can cause the alternator to stop charging effectively.

It’s pretty easy to tell if an alternator is faulty. It can look dry rot in the worst cases. Although if it has been slipping a lot, it will look shiny. You’ve probably heard it screech when you start the engine. Normally alternators do not fail silently..

Corolla Alternator Problems: Symptoms

Most of the time when an alternator is changed, the alternator itself is relatively inexpensive. It is the labor that makes the work expensive; you can learn here how to change an alternator. Well, here are the problems with the alternator of a Corolla and their most frequent symptoms:

1- Battery light

The battery light is designed to tell you that there is not enough voltage to charge the battery properly, or that the battery itself does not have the proper voltage.

On rare occasions the service engine soon light may come on. Also, some vehicles have a light “alt” which specifically indicates that there is a problem with the charging system, and not the battery itself.

2- Dead battery

Out of battery warning light, a dead battery is the most common symptom of a bad alternator on a Corolla. Since the alternator can no longer power your Toyota Corolla with an adequate power source, it will begin to draw power from the battery’s reserve.

Once this battery reserve reaches a certain level, the vehicle will begin to run erratically and will no longer start when the key is turned.

Sometimes the battery light comes on, the alternator is replaced, and then a few days later the vehicle dies. That is why it is important to test the battery before changing it. Almost all auto parts stores test the battery for free to see if it has a charge. The process can sometimes take an hour or so, but it’s worth knowing before you throw money away on a battery you don’t need.

3- Engine stopped

As described above, one of the problems with a Corolla’s alternator is causing your Corolla’s battery to drain quickly. If the battery becomes very depleted it will no longer be able to power your Corolla’s ignition system. Since the ignition system is no longer capable of producing a spark at full power, the engine will sputter and stall.

If you find yourself in a position where you suspect your voltage is dropping, but you need to get off the highway safely, turn off everything you can. Turn off the radio, daytime running lights, air conditioning, heated seats, ALL. That will allow all of the limited battery voltage to go to the ignition system.

4- Bearing noises

If your Corolla’s alternator begins to have bad bearings, it will begin to make some very unpleasant noises. If the serpentine belt has gone bad, it may still make some noises, but it won’t sound metallic like bad bearings would.

5- Lights of faint light

Dimming headlights is one of the most common signs of a bad alternator on the Toyota Corolla. Dim headlights indicate that the alternator cannot keep up with the power demand of the lights. As the Corolla begins to use up the voltage stored in the battery, the headlights will begin to dim.

6- Problems with electrical accessories

Many of a vehicle’s accessories require quite a bit of voltage. The heated seats, blower motor, power windows and even the radio will work erratically or not at all when the alternator is bad.

How to diagnose a bad alternator on a Toyota Corolla?

Alternator Failure In A Corolla
Toyota Corolla E160 Axio Prime

Some alternators wear out quickly, and others slowly lose their ability to charge under heavy loads. The ones that fail completely are easy to diagnose. The battery dies and you are stuck with a vehicle that is going nowhere.

The challenge is diagnosing an alternator that is not charging as it should. You can easily diagnose it with almost any multimeter.

After learning about problems that a Toyota Corolla alternator can cause, check out how to diagnose a bad alternator in a Corolla:

  1. get a multimeter. They’re cheap (you can get a decent one for $10), and you can get them just about anywhere.
  1. Set it to read voltage. Specifically, you will need to set it to 20V DC.
  1. With your Corolla turned off, you will connect the negative side of the gauge to the negative battery post or cable. You should then touch the positive side of the voltmeter to the positive battery cable. With the engine off, you should get a reading between 12.0 and 12.6 volts.
  1. Now that you have this baseline, it’s time to start the engine. Leave the air conditioning off, as well as the headlights and any other accessories.
  1. With the engine just started you should have more than 14.2 volts. If you have 14.2 volts or more, the alternator is charging fine. If you still see all 12, it’s time to replace the alternator. If it’s producing a voltage level in the 13’s, take it to a parts store and have it tested. It’s probably bad.
  1. Okay, assuming the alternator was producing more than 14 volts, go ahead and turn on the headlights, AC, radio, and any other accessories you can think of, and do the same test again. If the voltage dropped back to 12, that’s a very strong indication that the alternator is bad. Still worth a try, but be prepared to change it.
  1. Another test you can do that is not so scientific is to turn on the headlights and then start the engine. They should be brighter after the engine starts since the voltage is rising by almost 2 volts.
  1. Now, with the engine idling, accelerate a little. Have the headlights gotten brighter with increasing RPM? This is a very strong indication that the alternator has failed.

These tests rely heavily on you to notice very subtle differences in lighting. It should not be used as a substitute for checking voltage.

During the life of any vehicle, the alternator is going to fail. Good luck diagnosing your Corolla’s alternator.

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