how to test alternator when car won't start

(No, no lights were left on, I checked.) You’ve tried and failed to jump start your car. Today, you risk frying every electrical device in your vehicle. Check the voltage meter again. To differentiate between the starter and the alternator you can check the battery voltage – should be about 12.6 with the engine off and 13.5-14.2 with the engine running if the alternator is doing its job. If it doesn’t start at all, this means your battery is dead. Sign up for our newsletter! A simple test to check the working of the alternator is by running your car; and then unplugging the … Every editorial product is independently selected, though we may be compensated or receive an affiliate commission if you buy something through our links. An alternator typically lasts for 8-12 years, so it isn’t something that has to be replaced as often as other parts like the battery. If the vehicle won’t crank or start but the headlights are still working, look to problems with the starter or other parts of the engine. There are a few ways to test this to verify a problem: Turn your car on and let it run. If you have a newer battery but your car won’t start, you may have a bad alternator. Check out all the electrical system products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. First off, switch the key to the on position without cranking the engine. Listen carefully for a click. Next, notice whether dome or headlights seem dim, as this indicates a low battery. You depend on your car to get you where you need to go, so when it doesn’t start, it can be a pretty big problem. Alternator problems manifest themselves in various ways, depending upon the particular failure. The alternator is making rumbling or squeaking sounds. Complete DIY projects like a pro! Yesterday I took the car out, went into the store, came out and the car wouldn't start. You may have a failing starter. If you see higher readings, chances are the alternator is good. Sweet Begins Championship Defense with Win at Volusia, BMR Announces 2021 Lineup with Love, Moore, Bill McAnally Racing Earns Tenth Series Title, Elliott Races to First NASCAR Cup Series Championship with Win at Phoenix, Sweet Crowned 2020 World of Outlaws Sprint Car Series Champion. If your car won't start or your battery keeps dying on you, that doesn't necessarily mean there's necessarily a problem with EITHER your alternator OR your battery, although … Jump starting your car or truck does not turn over the engine at all. If your car battery works just fine after a series of check-ups, then your alternator is the problem. If the alternator is functioning correctly, it's likely that your dead battery was caused by a computer module that isn't shutting down when you turn off the car. If you’ve confirmed the battery is working properly after reading the section above, then the safest conclusion to make is the issue is related to the alternator. © Copyright National Automotive Parts Association. Turn the engine on. If your vehicle won’t start in the morning, your car battery could very well be the culprit. and connect the voltmeter’s positive probe to the positive terminal on the battery and the negative probe to the negative terminal on the battery. How do you know if it’s the alternator or battery? If your car will not start and you think you have a bad battery, alternator or starter, have your car inspected by a professional mechanic. Check the alternator You may be tempted to blame the battery — and you might be right — but alternator problems could also be at fault. We are no longer supporting IE (Internet Explorer) as we strive to provide site experiences for browsers that support new web standards and security practices. Here are a few tricks to try if the car doesn’t start: Family Handyman. This could also be caused by a dead battery though, so you’ll need to perform a test to see which is the culprit. The alternator is basically how a vehicle seems to have an endless supply of electricity. If it’s in the 13- to 15-volt range, your alternator is fine, and you need a new battery. The alternator generates the electricity for all electrical components, including the ignition, computer, power windows and locks, interior and exterior lights, as well as the radio. Get a cheap voltmeter. If your alternator isn't working, it's not going to keep the battery charged, so no amount of jumping will keep your vehicle going. We recommend our users to update the browser. Check the dash to see if your battery gauge is reading below 12V. While different batteries can have enormous capacities, eventually the headlights, heater, stereo and navigation would all drain the battery of power. If it doesn't and you need to jumpstart it again, drive it to the nearest automotive store and buy a new battery. (More sophisticated testing equipment is needed to detect an open or shorted alternator diode.). Next, you’ll need to jump-start your car with the help of a jumper pack or a friend with a running car. If you see higher readings, chances are the alternator is good. Still, using a few simple tests at home that show you how to test an alternator, how to inspect a battery, if necessary, and check a drive belt will help you pinpoint the cause of the problem. If the battery is working properly and nothing is wrong with it, then it's the alternator that will more likely cause a problem. Nothing happened at all, some lights came on inside and then dimmed right away. As mentioned above, if you find that your battery is low, it’s a good policy to check the alternator anyway. Connect the battery and the voltmeter to each other. Turn the ignition key. Learn how to test alternator with screwdriver at home with a few simple steps to always ensure the health of both the alternator and the battery. A dead car battery can be one of the first indicators of a problem with the alternator. I would not consider the alternator as the source of the problem but to check if you get the car started just take off the red (+) terminal and if it stays running your alternator is fine. In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck. For more information on problems with an alternator or battery, chat with a knowledgeable expert at your local NAPA AUTO PARTS store. Now the alternator does not actually assist with starting the vehicle, but once the car is running, the alternator does run all the car’s electronics and keep the battery charged. There are a number of reasons why this might happen, but one of the most common is that it isn’t getting enough electricity to start the combustion process. While this will tell you if your alternator’s good, it’s also really bad advice, as it can seriously mess up your car’s electrical and computer systems. It’s also critical to always make sure you address the root of the problem — not just the symptoms. All Rights Reserved. The above symptoms could also be signs of a weak car battery. Here Are the Warning Signs, If Your Car Battery Won't Hold a Charge, Try These 4 Steps, How To Use Sea Foam: Three Ways To A Cleaner Fuel System, Winter Car Tips: 5 Reasons to Dig Your Car Out of the Snow, 6 Signs You May Have a Bad Water Pump On Your Hands. Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter. Some starters will hum while they rotate and then click, while others will click shortly after you turn on the ignition. Always check the battery first, because it has a lower life expectancy (three to five years) and fails more often than the alternator. With the engine off, battery voltage should be between 12.5 and 12.8 volts. Knowing the difference will let you make a quick diagnosis and the proper repairs. First off, switch the key to the on position without cranking the engine. Running an overworked alternator causes more stress on the engine, making it to stall. A dead battery is your initial sign that something could be wrong with the alternator. Whining could just mean the belt is loose. There are a couple of ways to test for a bad battery or starter. The alternator can drain a battery over time and shorten its lifespan, and you don’t want to unnecessarily run through batteries on account of a bad alternator. Check the dash to see if your battery gauge is reading below 12V. If your alternator fails, your battery will lose its charge since the alternator won’t be able to keep it charged up. Once you’ve done this, let it run for about five to 10 minutes, then disconnect the jumper cables and try to start it up on its own. If the battery gets the green light, you know to inspect the alternator next. If you have a faulty battery, the car dies while driving won’t start and just clicks. If you don't have a battery tester, you can still see if the battery is good by jump-starting the car. Your email address will not be published. You won’t be able to check your alternator if you can’t start your car due to little battery power, and you’ll end up wasting precious time. Take the red lead and position it at the battery terminal on the positive (+) side. Check the voltage meter to make sure there is not a reduction in voltage with the electrical systems turned on. Conduct a Voltmeter Test. Try: Cycling the Key alternator, alternator failure, alternator problems, battery, charging system, electrical system. The alternator keeps the battery running after you start your car which is why your car doesn't die every time you turn it on and use the headlights or the radio. This Simple Hack Lets You Shift to Neutral, Failing Oil Pressure Sensor? Stay vigilant and know the signs of a failing battery or alternator, so you don’t end up stranded. Car won't start-- dead battery or alternator? Took it back to pepboys, they say everything checks out fine including the battery and the alternator and that it should work fine. If your alternator is healthy it sounds like you will be ok…just judging from how your battery accepted the charge from the last jump… that is promising news. The car battery is okay – your car battery is a clear indication if you have a faulty alternator. Dimmed car lights – whether it is your headlight or your dashboard light, if it starts to get dim then maybe your alternator … How to Temporarily Cover a Broken Car Window, How to Perform a Differential Flush on Your Car, How to Get Rid of Smoke Smell in Your Car, How to Make Cloudy Car Headlight Lenses Clear Again, We are no longer supporting IE (Internet Explorer), Guide to Choosing the Best Outdoor Curtains, How to Increase the Lifespan of Your Tires, Do Not Sell My Personal Information – CA Residents. Your email address will not be published. Go ahead and try turning the car’s key to the on position. If you connect the meter leads to the battery terminals and the meter shows that it's in the 13.8 to 15.3 volt ranges (engine running, lights and accessories off), that means the alternator is working as it should be. Related Post: How to Charge a Car Battery Without a Charger. As an alternator has rapidly moving parts, you might also hear noises if something is wrong. Always check the battery first, because it has a lower life expectancy (three to five years) and fails more often than the alternator. Stress test the alternator by turning on the car's radio, headlights, and air conditioner. How to Jump-Start a Diesel Truck With Two Batteries. If you live near one of our stores our automotive service staff will be happy to help you diagnose and fix such issues so you can get back on the road again! Required fields are marked *. Therefore, a piece of advice that often comes up is to remove the battery negative cable while the car is running and see if it shuts off. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test. With no battery in the circuit to act as a buffer, the alternator can put out up to 150 volts, depending on engine rpm. If you’re tempted to test an alternator by disconnecting the negative battery cable, don’t do it. Check the condition of the battery itself, noting any loose cables or crud accumulated on top. It should read between 13.5 and 14.5 volts. The second you disconnect the battery, the voltage regulator pegs the alternator to put out maximum power. Then start the engine and check for increased voltage readings. Hey guys, So 3 times in the last 2 days, my car has needed a jumpstart. Could it be a Bad Battery? Do they flicker? If it's below that, charge the battery with a battery charger before you conduct the test again. If the engine does not turn over, either your battery is completely drained or your starter is bad. Drive or run your car for about an hour or so, turn it off, and then restart it. When the smoke clears, that “simple test” could end up costing you several thousand dollars for new electronics. Growling suggests mechanical failure, like shot bearings. If the battery doesn’t start, check the battery with a voltmeter to determine the reading. If it's below that, charge the battery with a battery charger before you conduct the test again. Save my name, email, and website in this browser for the next time I comment. If you smell burning or see smoke in the area, that’s an electrical problem you need to address ASAP. Instead, observe your headlights when you try to crank the vehicle. Charge the batt… reinstall…start vehicle and test running voltage…and also test voltage with engine off… Report back. At What Temperature Does Diesel Fuel Gel? In the pre-computer days, you could pull it off without damaging anything. Wrong Signals Sensors: In modern cars, there are several sensors responsible for engine management. Or, if you are mechanically adept, try the following yourself: While the engine is running, use a multimeter to check the charge at the alternator output. What Is Gas-Line Antifreeze And Why Do You Need It? Take it to a professional for a final diagnosis. (Don’t touch the crud with your bare hands.). Test the alternator to make sure that it can start up the battery. You can get a good take on this by taking a current reading while trying to start. It takes a lot of juice to start an engine and meet all the various electrical needs of a vehicle. The battery, headlights, and/or interior lights seem weak. Your engine is cranking slowly or won’t crank at all. When folks have car problems, they often start with starting...or a lack thereof. If the car clicks when trying to start, but still won’t start, this can be caused by a weak battery, dirty battery terminals, a worn starter motor or a stuck solenoid. Then start the engine and check for increased voltage readings. With the engine off, battery voltage should be between 12.5 and 12.8 volts. Car Won’t Start Properly If your vehicle is having trouble starting or it’s cranking and turning over quite a few times before actually starting, then your alternator may be to blame. Took it to pepboys and they told me to replace the battery, a new battery later, my car wouldn’t start again and I needed to get it jumpstarted again. Being that the car couldnt be jumped stands out to me as being a severely drained battery or problems in the connection to your starter. If your alternator passes the voltmeter test, get your vehicle into a shop and pay a professional mechanic to find and correct the misbehaving module. For more information on car or … Automotive expertise from NAPA AUTO PARTS. If it starts, the battery is good. My Car Won’t Start and Battery Needs to be Jumped When you turn the ignition key, the expectation is for the vehicle to roar to life and all of your internal electronics to turn on. Car Won’t Start Symptom – Starter goes click. If the reading is not at the correct level, you might be looking at a faulty battery as the reason why you are having the “car won’t start after new battery installed” situation. Reasons Your Car May Not Start To determine why your car isn’t starting, begin first … If the alternator is working correctly, removing the battery from the system may cause a spike in voltage output, and possibly frying other components. How Do You Test an Alternator? Basically, your battery gets the engine going, but once it’s on, the alternator takes over and can, in theory, continue running the car without the battery’s help. The first step toward diagnosing a bad alternator is to test your battery with a multimeter or visit your local mechanic or dealership. Redlining a Car: 3 Common Automotive Myths Debunked, Garage Lighting Like the Pros: How to Stay Lit and Stay Safe. If it starts just fine and continues running for another five to 10, your problem is likely a dying battery. But that doesn’t rule out the alternator. That’s a sign of a bad alternator. If you tried jumping your car already and it either won’t start at all, or starts once but not again try this solution before resorting to buying a new battery or alternator. Dead Car Battery?

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