An alternator is a preferred tool among many vehicle manufacturers. It is the perfect replacement for the dynamo since it corrects all its shortcomings while performing additionally better. Some car owners with older models prefer the alternator and have replaced the dynamo with it in their vehicles. Understanding on how to test an alternator and check output will help you get ahead of the problems on your vehicle.
When should you test the alternator?
#1. The vehicle makes a cranking noise when started
When you start your car, it should rev up normally. If there is a problem with the output from the alternator, however, it will give out cranking noises when you start it. This indicates that not enough power is getting to the electrical components.
#2. Dim headlights
The headlights on the vehicle will not sustain a bright light when there is a problem with the alternator. They will get dim after a short while, indicating there isn’t enough power transmission. You can thus test the alternator to find out the output level and thus identify the causes of the problems.
#3. The battery becomes flat, often
The alternator should charge your battery by releasing the right voltage level and maintaining it. However, when it has malfunctioned, it will not release enough power to recharge the battery. It will become flat in a short while, and your car will fail to start.
#4. Regular jump starts
Your alternator could be damaged if your vehicle needs to be jump-started often. It shows there isn’t enough power supply to the electrical components causing this problem. Testing an alternator and checking output helps you identify the problem and correct it sooner.
Testing An Alternator with a Multimeter
A multimeter is the simplest way to test and determine the output from your alternator. These tools are also simple to find, and the digital options are easier to interpret. Firstly, ensure that you get the right alternator model from a certified vendor to ensure accurate and reliable results. It will measure all the electrical components on your vehicle and give you a reading to compare with the recommended minimums.
#1. Turn off the engine and make connections
The first step is ensuring your engine is turned off before you begin making any connections. It will prevent short-circuiting that could damage the electrical components of your vehicle. It will also render your readings inaccurate and thus unreliable. You can now connect the multimeter to the battery to test its output.
#2. Testing and checking output
The multimeter will record the voltage readings on your battery to determine whether it is receiving enough power from the alternator. This is a basic test, however, and will not necessarily show the state of the alternator. Read the readings displayed on your digital multimeter and begin interpretation.
The optimum reading should be between 12.5V and 13.5V. It shows that the battery is working well and has received a proper power charge from the alternator. It also shows you don’t need to replace the battery. However, if the battery registers a lower reading than these, it shows the alternator could be damaged and is not releasing enough output to power the battery. You will thus need to test the alternator comprehensively to determine its state and whether you will need a replacement.
Testing output using an Ammeter
Testing an alternator and checking output can also be done using an ammeter. It measures the voltage and ampere strength of the alternator, thus determining its working condition. This method is more effective on a Lucas ACR alternator as they have multiple pins and lack an earthing medium.
#1. Connecting the voltmeter
First, connect a voltmeter to the right terminals to get proper results from this test. The connection will vary for owners with a three-pin multiplug and a two-pin multiplug. Now, turn on the car and start the test. Connect the voltmeter to the pins on the Lucas ACR alternator independently and evaluate their results.
#2. Evaluating the output
The output on each pin should be almost similar. It should also range between the required 13.5V to 14.5V for a turned-on engine. Revving the engine and monitoring the changes is also recommended to ensure the evaluation of the results is accurate. If there isn’t a voltage reading on any of these connected terminals, it shows there is a problem with the voltmeter, and will need to be replaced.
Monitoring the Alternator’s state
Testing an alternator and checking the output is finalized by monitoring the state of the alternator in different conditions. Many modern vehicle models have an alternator gauge that will show the readings without connecting a voltmeter. First, check output while the engine is still. Note this down and test its changes when the engine is revved.
Here, run the engine close to 2000 rpm and check the output changes. The headlights are also expected to light brighter in this test, and it could act as a sign of the state of the alternator. If the readings sustain a 14V throughout this test, it shows that your alternator is working well. If it doesn’t record any changes, the alternator is damaged and will need a replacement or repair, depending on the extent of the damage.
Things to look out for while testing
There are various features you should look out for while performing the tests. They will ensure you get accurate and reliable results. First, test the tension on the vehicle’s drive belt before beginning the test. Ensure it is tight enough and will let the alternator charge your battery. Secondly, run through the cable connection to ensure it is done correctly. Here, you can look into the terminal connections to ensure they are in place. This step will prevent short-circuiting that can damage the vehicle’s electrical components.
Finally, while testing an alternator and checking output, ensure to interpret the results accurately. You can also write them down so as not to forget. This is the whole purpose of the test, and with incorrect figures and interpretation, you will not meet its essence. You can now enjoy a well-working vehicle once the tests are completed.