How to Check your Alternator
- Check the alternator gauge. If you have a volt/amp gauge, it will read the alternator output for you.
- Listen to the alternator while the engine is running. If there is a problem with the bearings you may hear a squealing sound coming from the front of the ...
- Turn the radio on and rev the engine. ...
- Find an auto-parts store that tests alternators for free. ...
How to check if alternator is good or bad?
- First, park the car in a public yet safe place. ...
- Open up the car hood. ...
- Now go back to the driver’s seat.
- Start the car engine. ...
- Get yourself out of that driver’s seat once the car starts running.
- Now go back to your car battery. ...
- Disconnect the positive terminal of the car battery while it is still running.
- Observe if the car engine is running like earlier.
How do you check for a bad alternator?
These are the basic symptoms of a bad alternator:
- The vehicle's (whether it's your car or a customer's car) instrument cluster has the battery light on.
- The vehicle has to be jump-started with another car or jump-start box (or whatever method).
- The vehicle will not stay running after the jumper cables/ jump-start box have/has been removed.
What are the signs of a bad alternator?
7 Common Symptoms of a Bad Alternator
- Battery light. The illuminated battery light on the instrument cluster is the first sign to the driver that there is an issue with the charging system.
- Lack of power or Limp Mode. If there is a complete loss of power, there is a good chance that the alternator failed. ...
- Noise. ...
- Broken Serpentine belt. ...
- Burning Smell. ...
- Bearing Issues. ...
- Bad Alternator or Battery. ...
How does an alternator know how much voltage output?
To ensure the correct amount, a voltage regulator determines when and how much voltage is needed in the battery. One of two types of regulators are found in most alternators: The grounded regulator works by controlling the amount of negative or battery ground going into the winding in the rotor, while a grounded field type works the other way around - by controlling the amount of battery positive.
How do you check the output of an alternator with a multimeter?
Conduct a Voltmeter TestGet a cheap voltmeter.With the engine off, battery voltage should be between 12.5 and 12.8 volts. If it's below that, charge the battery with a battery charger before you conduct the test again.Then start the engine and check for increased voltage readings.
How do I check the current output of my alternator?
1:3313:13How to test an alternator the right way! - YouTubeYouTubeStart of suggested clipEnd of suggested clipOkay it's simply you just connect it to the negative battery terminal and as you can see here theMoreOkay it's simply you just connect it to the negative battery terminal and as you can see here the battery is being charged at 10 amps.
How many volts should alternator put out?
between 13.9 and 14.8 voltsA good alternator should maintain battery voltage between 13.9 and 14.8 volts (14.2 is optimum). Even worst-case, with all accessories turned on, there should be at least 13 volts at the battery.
How can I test if my alternator is working?
A simple test to check the working of the alternator is by running your car; and then unplugging the positive connection of the battery. If the car stops, then you most likely have a problem with the alternator. Another simple test is to check your interior lights.
How many amps should an alternator put out?
Alternator ratings range from about 60 or 70 amps up to 150 amps or more on many late-model vehicles. Some high-output alternators can generate upward of 200 amps. The amp rating of the alternator is matched to the vehicle's electrical system.
How do you check an alternator without a voltmeter?
You can still check an alternator without a multimeter if you don't have any available.Start the car and rev the engine to 2000 RPM. ... Open the hood and listen closely to the alternator while the engine is idling. ... Switch your car radio to the lowest frequency on the AM band, then lower the volume.More items...•
Is 14.7 volts too high for alternator?
To fully charge in reasonable times, alternator output must be 14.2 V to 14.5 V as measured right across the battery posts. Above 14.5 volts charging voltage, batteries have a greatly increased tendency to release excessive acidic vapors, hydrogen gas, and to corrode things around the battery.
How many volts should a 12 volt alternator put out?
13-14 voltsA car alternator needs to be putting out at least 13-14 volts (ideally between 13.8 and 14.2 volts) to effectively charge a 12 volt car battery.
How do you check an alternator without starting?
1:252:24How to diagnose a No Start Condition - Alternator - YouTubeYouTubeStart of suggested clipEnd of suggested clipSo let's go ahead and do that real quick our pulley is spinning on our alternator. So this looksMoreSo let's go ahead and do that real quick our pulley is spinning on our alternator. So this looks great we determined that our alternator.
How can I test my alternator at home?
More videos on YouTubeGet a multimeter.Set your multimeter to DCV (DC Volts) above 15.Make sure your alternator's positive and negative terminals are clean.Put the multimeter's black cable to the negative terminal and the red cable to the positive terminal.Look for an ideal alternator reading of around 12.6.More items...•
How do I know if it's the alternator or the battery?
If your engine won't turn over or takes far longer than usual, it's time to grab the jumper cables and attempt a jump-start. If your engine starts and stays running but won't start again later, it's likely a battery problem. If your vehicle immediately stalls, it's probably a bad alternator.
How to check alternator output?
Check the alternator gauge. If you have a volt/amp gauge, it will read the alternator output for you. Run engine at 2,000 rpms for tests and turn on the blower fan for the AC or Heater, the headlamps, and any other accessories that put a strain on the alternator, and watch the gauge to see if it decreases voltage or amperage. As a rule, if the voltmeter is higher when the engine is running than when the engine is not, you can confidently assume that the alternator is charging.
How to test alternator?
The easiest way to test it is by using a voltmeter. If you're well in tune with your car, there are a few other methods you may try as well. This test is to give a general health of your alternator and battery. Some newer vehicles may have computer controlled charging systems and would require additional testing. Steps.
Why do you need to check the battery before checking the alternator?
If the weather is cold or your battery is old, your battery could be the issue and your alternator might be just fine. That's why you need to check the battery before checking the alternator. Here's how to do it: Turn off the car. You'll want to make sure your engine is off before attaching the voltmeter. Open the hood.
How many volts does an alternator need to charge?
Repeat the process with the lights, radio, and AC on. The alternator is charging if the battery voltage stays above 13 volts with the engine at 2,000 rpm and all accessories on.
What does it mean when your alternator is overcharging?
If the reading stays the same or drops, that means the alternator isn’t charging and you may need a new one. If the reading is more than 2 volts higher, that could mean that your alternator is overcharging.
What does a multimeter measure?
If you have a multimeter, you can use that instead. A multimeter measures voltage as well as other electrical properties such as current and resistance. You want to measure voltage when you're checking your alternator.
How to connect a voltmeter to a battery?
You'll want to make sure your engine is off before attaching the voltmeter. Open the hood. Connect the voltmeter to the battery. Place the red lead of the voltmeter to the positive battery terminal and the black lead to the negative terminal. Avoid touching your skin to the battery.
How to check if alternator is working?
Check the amperes your alternator produces if it operates correctly. Look in your car's manual and go to the specification section: it's usually at the back. Turn to the page for your alternator details. It tells you the minimum and maximum amperes from the alternator. The minimum is when you are using items that consume small amounts of energy, such as your car stereo. The maximum is when you turn on major energy consuming items. Make a note of the two figures.
What to do if alternator reading is 10 percent?
If it's more than 10 percent higher, check to make sure no electrical equipment is turned on and if it isn't, get it checked by a professional.
Why is it important to know the ampere output of an alternator?
The correct ampere output from your alternator is important as amperes are the current that powers the electrical items in your car. Items such as heater-fans, wipers and headlights use high amperes and, when you turn them on, your alternator has to adjust its output to meet the energy requirements. If you find that your lights are dim ...
What to do if your alternator is below the maximum?
If the reading is more than 15 percent below the maximum, check you've turned on as many item as possible. If you have, then you need to get the alternator checked. If you haven't, turn on more equipment and check the reading again. If there's little or no change then get your alternator checked.
How to read amperes on a battery?
Use a multimeter and set it to read amperes. Put the metal prong on the end of the black wire that extends from the multimeter onto the negative battery terminal. The negative battery terminal has a black cable attached to it and is labeled "Neg." Put the metal prong on the end of the red wire onto the positive terminal of the battery. The positive terminal has a red cable attached to it and is labeled "Pos."
What is the best way to turn on the energy in your car?
Turn on energy consuming equipment in your car: air-conditioning, wipers and lights are good. The more you turn on the more amperes are needed to power them so your alternator adjusts the output, if it's operating correctly.
What to do if your alternator needs replacing?
If you find your alternator (s) need replacing, place a bulk order on new alternators so you don’t run into vehicle downtime and loss of productivity.
What is the warning light on an alternator?
Many instrument clusters include built-in voltmeters, and some vehicles include dash mounted warning lights that illuminate when alternator output drops below a set level.
What happens if the voltage is too low?
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 many volts should a negative lead be?
This can be any metal component with proper grounding, with the exception of the alternator housing itself. Output voltage should be around 14 volts (13.8 to 14.5 depending upon the application) with the engine running.
Does voltage tell the whole story?
But voltage doesn’t tell the whole story. Any responsible and thorough alternator testing procedure must also include a measure of the amperage output. A clamp-on ammeter is a great tool for completing an accurate test.
Can you check the alternator output at the battery?
You can check the alternator output at the battery only as part of completing a thorough test.
Can you use an ammeter to test an alternator?
You can purchase an electronic alternator amperage tester for your shop use a clamp-on ammeter.
How to check 13.5V-14V?
Test the battery and look for 13.5V-14V with the engine on and all accessories off including lights, a/c, and radio. This can be done at the battery terminals with a quality digital volt and ohm meter. This should be a normal reading for these setups. If you do not have access to a DVOM, then you can remove the alternator from the car and most local auto parts stores will test these for free.
What voltage should a batter be?
Test the battery voltage, at rest this should read between 12.5 and 12.8V on average. If the batter is low, then charge the batter to meet these specs.
What happens if your car's charging system is not working?
When your car's charging system is not performing up to par, you run the risk of being left stranded on the side of the road. When you see a battery light pop up onto your dash, you know that there is some type of fault in your charging system. If your battery is fairly new, the most likely culprit is your alternator.
How to check the health of an alternator?
“With the car running, you can turn on all the heavy loads; turn on the heater blower motor, turn the lights on, etc.,” he tells us. “Then check the voltage at the battery terminals. That’ll give you a general idea of the health of the alternator.”
What is the best way to test an alternator?
At minimum, we recommend picking up some sort of multimeter to help test out your alternator. A multimeter is a handheld device used to measure voltage and test electrical connections. Affordable examples can be found both online or at your local auto parts store. Here’s one we love:
How to check battery voltage?
Simply check the voltage of your battery by touching the multimeter prongs to the terminals with the car shut off. Take note of that number; it should be somewhere in the 12-to-13-volt range, according to Hines. Then, start the car and check the voltage at the battery again while the vehicle is running.
What does it mean when an alternator doesn't work?
If it does, that means the alternator is still producing sufficient voltage to at least keep the engine firing, according to Hines. If it doesn’t, that means the alternator isn’t producing enough voltage.
Why does my alternator keep dropping?
If the number has dropped significantly compared to when everything was turned off, it could be a sign your alternator can’t keep up with the electrical system’s demand.
Where is the alternator located?
Your alternator is arguably one of the most important parts of your engine. Usually found attached to the front of the block, it’s responsible for keeping your battery charged as you drive down the road. Without it, your battery would quickly run out of juice, leaving you stranded.
How much does a load tester cost?
Proper load testers, normally found at professional shops and dealerships, cost around $2000 on the low end, not exactly cheap enough for the average DIYer. But there are still a few low-budget methods you can try to give you a good idea of the health of your alternator.
What if the Alternator Tests Fine?
Keep in mind, just because the Alternator tests fine, does not mean the system is fine.
How many volts does a car alternator have?
What this means is that voltage at the Alternator may be, say 14.5 volts. Voltage at the battery may be 14.2, but yet, way out at the rear taillight bulb, this voltage may only be 13.5 volts, due to voltage drop.
What is a multimeter used for?
Much like testing your car battery, a multimeter can be used to quickly tell whether your car’s charging system is adequately keeping the car battery at the proper charge, and operating the electrical system at the proper voltage as well.
Why does my car's charging system have a higher voltage than the battery?
For one, a phenomenon known as voltage drop causes voltage at the source (the alternator) to degrade as it travels through the hundreds of feet of wiring that snake throughout a vehicle.
How many volts should a multimeter be?
Set your multimeter to voltage and ensure it’s adjusted to 20 DC volts, or if your voltmeter does not have incremental settings (2,20,200,2000) then simply set it to DC volts.
What voltage should a car battery be?
In most cases, on most vehicles, you will see a voltage of 14.00-14.5 when the vehicle is running, with all accessories off. Now that you know this, it’s time to test the charging system.
What does it mean when the battery light is illuminated?
Contrary to what may seem like a bad battery, an illuminated battery light does NOT mean the battery is bad, it means the battery is not being charged properly.
What does an alternator sound like?
The alternator is making rumbling or squeaking sounds.
What Signs Indicate a Weak Alternator?
Before you test your alternator, here are some signs that your alternator might be weak:
What voltage should a car battery be?
If you’ve run your car for a long time and while the vehicle is running, the voltage reading is in the 13-14 volt range, but then you shut the car off, and the battery voltage instantly drops to well below 12 volts (10 volts or under; 9 volts or under in freezing weather conditions), it is likely that your battery needs maintenance or replaced.
How many volts does an alternator need?
A car alternator needs to be putting out at least 13-14 volt s (ideal ly between 13.8 and 14.2 volts) to charge a 12-volt car battery effectively.
Why isn't my alternator charging?
The alternator isn’t charging the battery because of other vehicle problems like bad wiring connections, bad battery cables, a bad battery or a bad PCM. Save yourself the embarrassment and hassle of a comeback and test the alternator wiring connectors and wiring harness. You can do this by using your voltmeter to run “voltage drop” checks ...
What does a voltage drop across a voltmeter mean?
If there is resistance in the connection, some of the voltage will bypass the resistance by flowing through the voltmeter. A reading of more than 0.2 volts means trouble. Ideally, the voltage drop across any connection should be zero or less than 0.1 volts.
How to check if alternator belt is loose?
Locate your alternator and check to be sure the alternator belt isn’t loose. Step 2: Turn your multimeter to the 20 V setting. Step 3: Start the engine. At this point, check to make sure the alternator pulley/belt is spinning correctly without slipping.