Where To Connect Your Voltmeter
- The positive lead of the voltmeter should connect to the positive output terminal on the alternator.
- The negative lead should be grounded. This can be any metal component with proper grounding, with the exception of the alternator housing itself.
Output voltage should be around 14 volts with the engine running.
If you check the voltage at the battery under the same parameters, you should not have more than a half volt drop between your result at the alternator and the result at the battery.
If the voltage is higher by more than 4 volts, the regulator may need repairs or replacing. If the voltage is low, the alternator may be on its last legs.
Low voltage also comes from poor electrical connections, a loose drive belt, low engine idle speed, or poor ground.
How Can I Test My Alternator
In the past, it was common for people to try and check their alternator by disconnecting the negative battery cable. Our advice: Dont do it you risk burning out every electrical device in your vehicle because when there is no battery to act as a buffer in the circuit, the alternator can put out up to 150 volts, depending on the engines rpm. This easy alternator test could cost you thousands of pounds in damage. There are, however, a couple of simple and safe alternatives to test your alternator.
Tests To See If Alternator Is Bad Or Not
OK, lets get started. The test works in this way: You’ll be using the vehicle’s dome light to diagnose the charging system. You can do this test by yourself or you can have someone helping you.
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What Is The Serpentine/drive Belt
The serpentine belt is also known as the drive belt. A drive belts function is to drive accessories installed on your engine. The drive belt will control and provide power to the alternator, water pump, and air conditioner compressor. If the serpentine belt breaks down or is damaged, the car wont be able to drive. If you try to run the engine without the drive belt working, the engine would overheat, since the water pump isnt working. The broken belt can also damage the radiator and coolant hoses.;
Symptoms of a broken drive belt include loud noises, squealing noises, and other sounds coming from beneath the hood. The charging system warning light could also come on since the alternator will stop charging the battery. A bad alternator and a bad drive belt go hand in hand.;
How To Easily Diagnose A Bad Alternator At Home
A significant part of your cars operational mechanisms are powered by electricity rather than the fuel-powered engine. To run all the electronics in your car, it has an alternator. This can be thought of as an electric generator that converts engine power into electricity.;
There can be several situations where the alternators might not work like theyre supposed to and that can result in serious problems. You need to know how to check your car alternator so that you can diagnose it.;
Before that, it is important to understand how the mechanism of the alternator works. Only then will you know how to test the car alternator.
DISCLAIMER:All the information is provided in good faith to help you diagnose the issues with your cars electrical system. Work on your car with care and if you need assistance, please seek help from a professional.
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How A Car Battery Works
Before we guide you on how to test a car battery, it would be a good idea for you to understand more about how your cars battery and electrical system work. As mentioned, your cars battery is responsible for mainly two things: powering up the starter motor when you turn the key and powering the electrical components in your car. Thats why when your battery is dying, you will have difficulty starting your car. It may not even start at all if the batterys completely dead. But how does the entire system work?
Cars nowadays use a 12-volt lead-acid battery, which creates electricity from the chemical reaction between lead and acid. When the engine is off, everything electrical in your car runs from the electricity in the battery. Once the engine is running, your cars alternator will power all the electronics in your car. It does this while also recharging your battery, making sure it has enough electricity the next time you need to start your car. Thats why when you have a bad alternator, your battery may die more quickly.
A cars battery typically lasts between 2-3 years, depending on the battery quality. Cars with a stop-start system may also drain the battery more quickly. If your cars battery is dying or has died prematurely, this is usually because your alternator isnt charging the battery properly. Thats why well guide you on how to test a car battery, as well as the alternator.
What Is An Alternator
To fully understand why an alternator should be tested, it is important to understand what an alternator is and what it does.
People usually associate the cars electricity with the car battery, which is intuitive and correct. However, to make all the components that are powered by electricity work, the alternator must work.
In short, the function of an alternator is to generate electricity to recharge the battery and power the electrical components. It does so by converting mechanical energy into electrical energy.
The battery stores energy, enabling you to start the car. If it were not for the alternator, your battery would be drained within an hour as it would be the only source of electricity.
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How To Test An Alternator: Problems Defects Symptoms
Alternator problems could leave you stranded on the road side. Regular testing is the only way to prevent this there really is no other alternative.
Fading headlamps, the dying sound of the radio, heating or air condition systems not working, and even cars failing to start. These problems, like many others, are almost always said to be caused by a cars battery being flat or being faulty.
But car batteries have been taking the blame for too long and they often arent really responsible. The batterys only true job is to start the engine. As soon as the engine is on, all of the energy for the electrical systems comes from the alternator. The alternator also has the task of charging up the battery, so even a flat battery not letting you start the car is really the fault of the alternator. Lets find out exactly what the alternator is and what an alternator check or alternator test to sort out some common alternator faults might look like.
Warning Signs Of Bad Alternator Or Bad Battery
Every vehicle has a battery warning light on its information panel which usually comes on when the engine is ignited. This battery warning light automatically goes off when the engine starts. In the event that it persists even after the engine has started, then, there is a problem with the vehicles charging system.
This translates to a fault with the alternator or battery.
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Signs Of A Bad Alternator
If the above steps reveal that the battery is working, its time to take a closer look at the alternator. There are certain bad alternator symptoms to look for, find out how to tell if your alternator is bad:
Fixing your battery or alternator can be an expensive repair. See how you can find the right mechanic to work on your vehicle. Make sure you have roadside assistance so you can get help if your car wont start.
How To Test Alternator Withscrewdriver
In you want to learn how to test alternator with screwdriver, then follow these steps:
- Please insert vehicle key on theignition switch without starting the engine.
- Before accessing the alternator, openvehicles hood so you can test alternators current.
- You are to test the magnetism of thealternator, so put the metal screwdriver close to the bolt on the alternatorpulley.
- You can then turn the key of your carto the on position without starting the car. This will activate the voltageregulator, put the metal side of your screwdriver close to the nut on thealternators pulley, you will observe a high magnetism which should pull thescrewdriver. If this happens, it means the alternator is perfectly working, butif it didnt, it means your alternator is not working perfectly.
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What If A Car Alternator Fails
If the alternator fails while you are on the road, do these things:;
- Turn off any of the electronics that you can. This includes the infotainment system, the air-conditioning, and the 12-volt outputs.;
- Drive smoothly and try not to engage the brakes very often because modern car brakes need electric power to operate.;
- Avoid heavy traffic. Stopping and moving puts strain on the electrical systems of the car. If you are in heavy traffic, pull to the side, and wait for the traffic to decrease.;
- Head to the nearest service station and get the problem fixed.
If the signs are not severe and you just feel that your batterys performance is progressively deteriorating, you can determine if it is the alternator or the battery that is faulty.
Lets see how to test the car alternator to make sure it is the part that has the problem.
Battery Warning Light On Dash
When the battery warning light pops up on the dashboard, its commonly mistaken to be a battery-specific issue. However, the battery warning light indicates that there could be a problem within the wider electrical system of your car, including the alternator.
Alternators are designed to work at a specific voltage, typically between 13-14.5 volts. If your alternator is failing, its voltage may drop below capacity, causing the battery warning light to appear on your dash. Similarly, the battery light will also appear if the alternator is exceeding its voltage limit, depending on how much stress it is under.
Depending on the electrical load from your cars accessories , you may see the battery warning light flicker on and off as the alternator fluctuates in and out of its intended voltage capacity. While this may seem like a minor annoyance, its better to bring your car in for an alternator inspection rather than wind up stuck on the side of the road.
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How To Test Alternator With Multmeter
Before you will test alternator with multmeter, ensure your car battery is completely charged. Then remove the negative lead from the multmter and place on the negative post of the car battery. After which, insert the meters positive lead on the battery positive lead, and set the meter to DC voltage making use of 20 scales and then observe the display to make sure the battery is completely charged.
You can thenstart your car to find out what your alternator is generating. Note that thatreading should increase, but if not, then it means your alternator is notgenerating current. You can now turn on your heater blower and light toexamine, if the alternator is not strong enough, then allow your vehicle to runfor some time and once it reads, it means your alternator is in perfectcondition.
How To Test A Car Battery: 2 Prepare And Connect The Multimeter
The multimeter has several settings for different tests. To test a battery, what you want to do is to set it to the 20 volts setting. Simply rotate the dial on the multimeter and youre good to go.
The next step is to connect the multimeter to the battery. The multimeter will have two probes: red and black. Simply connect the red probe to the positive terminal and the black probe to the negative terminal. Make sure that the probe and the battery terminals are in contact.
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Check Serpentine Belt Tension
The serpentine belt needs to be under the correct tension to provide traction to the alternator pulley. The amount of free play allowed in the serpentine belt varies from car to car but if you can push it easily with your hand, the belt does not have enough tension to correctly operate the alternator.;
If the serpentine belt is under the correct tension and the alternator pulley is spinning, you need to make sure it is putting out an electric current. Heres how you can do that.
Common Issues And Symptoms Of Bad Alternators
Since the alternator is made up of moving parts which are subject to heat and dirt or can become worn out over time, there are many issues that can result in an alternator going bad. Common alternator issues include loose mounting bolts or bearings failure due to exposure to heat and dirt. When this occurs, the alternator usually makes a grinding noise because the parts within the alternator cannot spin efficiently without proper bearings. An auto alternator test enables car owners and auto technician to ascertain the cause of their alternators problems.
Regardless of the underlying problems or common issues, you will most likely recognize these symptoms whenever your alternator begins to malfunction:
| Headlights are dim when you start your car | Charging system warning light is on | Can’t start engine without a jump-start box |
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Engine Is Slow To Crank
Not everyone will notice this, but keen drivers will almost certainly notice it. Most cars will crank and start the engine easily. But if youre battery is dying, it might crank slower and it will sound like the engine is struggling to come to life. If you notice that your engine is struggling to crank, then your battery is starting to die.
Related Questions And Answers
How Much is an Alternator for a Car?
If you find yourself wondering, how much is an alternator for a car, here is a quick rundown of the costs. Replacing an alternator can be fairly expensive. The total cost will depend on the vehicle you are driving, as well as if you choose a brand new, or a rebuilt alternator. If you can do the work yourself, a rebuilt alternator can cost as little as $80 for older vehicles. An alternator for a newer vehicle can run $150 to $200. If you need a professional to install your new alternator, budget between $300 and $500, depending on your car. High end sports and luxury cars will cost even more.What are the Main Components of an Alternator?
The alternator helps maintain the voltage of the car battery. There are four main components of an alternator. The stator and rotor are belt-driven magnets encased in copper wiring. They create a magnetic field. The belt is driven by a pulley that connects to the engine. This spins the rotor and creates a magnetic field. The stator uses this to create voltage and electricity which flows to the diode. The diode assembly than converts the AC electricity to DC, which is used by the car battery. Finally, the voltage regulator acts as a surge protector for the alternator.Where Can I Find Second Hand Alternators for Sale?
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How To Check Your Car’s Alternator
Joel Ilton
If youve recently replaced your battery,;but are still having issues starting your car, the problem may lie with your alternator.
The alternator supplies the vehicle with power while the engine is running and also charges up the battery.
This is an integral part of your vehicles operation, and if it fails, can leave you stranded. Here is a step-by-step guide on how to check the output of your alternator.
The first step is to find yourself a multi-meter. These are relatively inexpensive and can be picked up from an auto parts store, such as Supercheap Auto.
You will need to set the meter to volts by turning the dial to the voltage icon. The next step is to locate the battery in your vehicle.
This is usually located under the bonnet of the car, but can be located in the boot, or in some European vehicles, under the passenger seat!
Once you have located the battery, take a reading of the battery voltage with the car turned off, to give you a base reading.
Take the black and red probes of the multi-meter and place them on the corresponding battery terminals. You should get a voltage reading displayed on the screen of the multi-meter. A good battery should sit around the 12 volt mark.
Once you have the battery voltage, it’s time to start the car. Once the vehicle is running, place the probes on the battery terminals.
A good alternator will be putting out around 13.9 to 14.3 volts. If the reading is below this, it may be that your alternator is on its way out.
