how to use a multimeter on a car alternator

But there’s a problem: The battery and the rest of the car’s electrical system use direct current (DC). Then remove the negative lead from the multmter and place on the negative post of the car battery. As the word implies, resistance is the tendency of a conductor to resist current. On the positive side, the wire going from the battery to the clock is broken up. In this guide, I’ll be referring to my own multimeter and using that as our example throughout this guide. Unless you are measuring a flame rod or thermocouple you very likely will not need to find thousandths or (good grief!) Make sure your work area is well-lit (sunlight and battery-powered lights) and cleared of obstructions so that you can move freely. Plug the black probe jack into the COM outlet on your multimeter. Set the device to read DC (direct current) voltage. If it’s in your car or in a battery-powered device, it’s probably DC. A lightbulb is a high-value resistor. Otherwise, you run the risk of damaging your multimeter.Here’s why: When you select the ohms reading, the battery in the meter sends a small voltage between your two probes, which is how the meter reads resistance. So just stick the red probe in the A jack. So if you have your multimeter set to 20 in the DCV section, the multimeter will measure voltages up to 20 volts. Take a look at the reading on the screen. Did you read at least 12 volts DC? If yours is auto-ranging – you can ignore steps #3-5. If your car is having trouble starting, you can check the ignition voltage with your multimeter. As multimeters go, this little unit has all the unique features of most of its “High End” rivals and at a price which is very affordable. Fun Fact – Some resistance is planned. Diodes only conduct current in one direction, so if your probes are on the wrong terminals, you will either get a zero reading or an unreasonably high resistance reading. This is also a great way to prove a wire has continuity or is unbroken between two points. If the voltage doesn’t increase to around 14 volts or so, then it’s likely that the alternator is having issues. This will give you a more accurate reading. The current flows around that “circle” in a circuit beginning at the breaker or fuse in your electrical box and then returning on the neutral wire. Craig Lloyd is a smarthome expert with nearly ten years of professional writing experience. Still, there will always be some resistance. The symbol for DC is a solid line with a dashed line below it. Place the black lead on the negative post and red lead on the positive post. We’ll be measuring the voltage of a AA battery, the current draw of a wall clock, and the continuity of a simple wire as some examples to get you started and familiar with using a multimeter. Amps, which is short for “amperes”, is what we call the unit that measures electric current. The alternator's job is to produce electricity and charge the battery. If the pressure driving the water (psi) is like voltage, then the quantity of water (gallons per minute) is like current. For example, If your probes are on either end of a fuse then it will measure the resistance of the fuse. If you were to introduce 100 volts through that circuit, you would surely damage something. Somewhere a pump is pressurizing that water so it flows with force. A multimeter itself is going to do one thing – measure voltage, and in this case, DC voltage. The readout on the screen will instantly read “1”, which means that there isn’t any continuity. While most multimeters can also measure alternating current (AC), it’s not really a good idea (especially if its live power), since AC can be dangerous if you end up making a mistake. Testing the Alternator When You Don’t Have a Voltmeter . There’s really not one single multimeter that you should shoot for, and it really depends on what features you want (or even features that you don’t need). Furthermore, start your car up and rev it up a bit. We’re going to explain everything here. If on the other hand, there is a break somewhere along the line, what would you read? Power up the receptacle or component for which you are testing voltage by either closing the breaker in your breaker box, turning the ignition in your car, or turning on the battery-powered device. A car battery puts out between 12 and 14 volts, so if you’re only working on the car this is much easier than working on home appliances or wall electrical outlets. Vehicle 1 solid 14.8 with minimal fluctuation to .7 or .9. If you’re not getting a clear reading, turn the selector to the next highest setting until you have a recordable number. Check the battery first This is for the protection of the multimeter, in case your next measurement requires greater current. In essence, it’s about the number of electrons passing by a point over a given time period. Many sensors and sensor circuits use a lower voltage, typically 5 volts, while the ignition coils generate a very high voltage (5,000 to 35,000 volts) to fire the spark plugs. You can use the amp setting on your multimeter to determine how much current is flowing through a circuit. Does water flowing through a hose experience resistance? Well, in this case with the AA battery, we’re checking to see if it has any juice left. I’ve been looking everywhere on how to trouble shoot issues using a multimeter safely and how to understand the numbers shown. RELATED: The Different Kinds of Electrical Outlets You Can Install In Your House. If the car has an intermittent misfire, you may be able to trace it to one of the leads. Plug the black probe into the COM outlet found on the multimeter. Now let’s check your alternator with a multimeter: Do the same test as above with the car running. We can also find: At first glance, the parts of a multimeter may look complicated. Before you learn how to test a car battery, there are a couple of things to keep in mind. I’m pretty sure it’s a safety switch stopping the mower from starting but need to identify which one. It gives current such a hard time that the lightbulb gets very hot until it glows. What Can You Use a Multimeter For?4. The component you measure should also be disconnected from any batteries or external power source. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites. In this article, let’s assume you want to use a multimeter. Well, it’s because it’s a combination of a voltmeter, ammeter, and ohmmeter giving you the power to measure: If you have some simple electrical work to do around the house, and you don’t want to hire an expensive electrician, why not give it a try yourself? You can clip the probes to the circuit before powering up the device or turning on the breaker. A multimeter has a positive and negative lead. In a more practical situation, you could do this type of measuring on a car battery to see if it might be dying or if the alternator (which is what charges the battery) is going bad. High or low resistance? How to Use and Read a Multimeter to Measure Voltage7. Figure 5 – Alternator leakage current. Furthermore, measuring anything over 10 amps could blow a fuse or destroy the multimeter as well. In this case, we know the AA battery has a very low voltage, but we’ll start at 200 volts just for the sake of example. Multimeter dials are marked as following: Each category on your dial switch might have multiple settings for various ranges (Unless you have an auto-ranging meter. The amount of resistance in a circuit can be measured by your multimeter. The steps above tell you how to use and read a multimeter in safe conditions. I’ve watched a ton of YouTube videos but I really liked this explanation. It would be low since the wire is continuous. Granted, you will get more accurate readings using probes since they can detect much smaller amounts of current such as milliamps and microamps. However, if you’re measuring voltage and current from your house outlets, then you’ll want to use a higher range. When we’re done, you’ll have a firm grasp on the essential functions and benefits of this indispensable tool so you can bang out those projects you’ve been putting off. How to check the alternator with multimeter. Identify the underlying cause of the whine to silence it for good. Thanks for your kind words. The ohms setting is a safe way of proving continuity before applying high voltage. Your multimeter can measure current (amps) too. Voltage is easier understood as “pressure”. There is friction between the water and the surface of the hose. This protects the wire from overheating which would be a bad thing. Your multimeter will also have two or three ports for plugging in the probes (pictured above): Warning: Make sure that if you’re measuring anything with a current higher than 200mA, you plug the red probe into the 10A port, rather than the 200mA port. If you were to ever set the selection knob to a number value lower than the voltage of the thing you’re testing, the multimeter would just read “1”, signifying that it’s overloaded. So, why would you need to measure resistance? This setting is usually denoted with the battery symbol. Plug the red probe jack in the appropriate current outlet, either the high current (A) or the low current (mA or µA). 4. If your multimeter probes have clips, this provides additional safety. You would read zero or a small fraction of 1. All Rights Reserved. If there is a complete circuit, your multimeter will either beep, show a “0”, or something other than a “1”. So the wire feeding the circuit must be opened and the meter probes placed across the gap. Turn the selection switch to resistance, or. Volts DC – The symbol for DC is “⎓”, this is the most used setting for automotive applications. When start your car, the charging system of the car is working in a normal way. This guide is meant to be a starting point to get you up and running, and it’s very possible that some things shown above are different on your particular model. Going back to the water example. So why is this tool called a multimeter? 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.. Anyway, let’s get started actually using a multimeter. However, I want a more accurate reading, so I’ll move the selection knob lower down to 20 volts. An alternator helps power all of a car's electrical systems, including the starter motor, speaker system, and lights.A bad or failing alternator can discharge your battery, cause issues with your car's electrical systems, or leave you stranded when you need to use your car.. As you know, if the circuit of current is ever broken, electricity stops flowing and lights, outlets, etc quit working. Turn the selection switch to the appropriate voltage. The voltage category might be further divided into AC voltage and DC voltage. There is a force being applied even though there is no flow. A clamp multimeter is a multimeter with a special hinged jaw. Resistance measurements will always be measured Your meter will measure the resistance it “sees” between the 2 probes. At the bottom of the multimeter, you’ll usually find the jacks for your testing probes. 5. Select the DC volts position on your multimeter (or the 12V setting if you have a dedicated car battery test range). Where a battery test at AutoZone has an advantage is it’s going to simulate a … Continuity means that current can flow uninterrupted from one point to another. In any case, here’s a rundown of what each symbol means on my multimeter: Your multimeter might also have a dedicated setting for testing the amperage of AA, AAA, and 9V batteries. Make sure the display activates. ... Signs of a Bad Alternator. Vehicle 1 - Alternator replaced in last year, battery within two years. Set the selection switch to the highest resistance range to start your measurement. You simply clamp the jaw around a wire, select amps on the dial, and the digital display will tell you how much current is passing through the wire. In the water hose example, a pressure gauge calculates the force so you know the strength of the water current if allowed to flow. Start by turning on your multimeter, plugging the probes into their respective ports and then setting the selection knob to the highest number value in the DCV section, which in my case is 500 volts. If you don’t know at least the voltage range of the thing you’re measuring, it’s always a good idea to start with the highest value first and then work your way down until you get an accurate reading. For example, if you want to measure the current in a circuit with an outlet receptacle, you could, b) Place the red lead from your meter on the disconnected wire, c) Place the black lead on the plug terminal where the live wire was before, d) Make sure you’re not touching either of the exposed parts of those leads. You may want to try and start the car and then disconnect one of the battery terminals. So if I were to set the knob to 200 millivolts (0.2 volts), the 1.6 volts of the AA battery is too much for the multimeter to handle at that setting. Now, this is where it gets messy. How to Use a Multimeter to Test a Car Battery. Learn how a multimeter works. This jack should be marked with an, The third red probe jack (outlet #4) is for measuring voltage, resistance, diode, capacitance, frequency, duty cycle, and possibly temperature. It's a good idea to know a few simple tests and early signs of alternator failure to avoid a breakdown. If you’re testing a capacitor, make sure it’s discharged in order to prevent electrical discharge into your multimeter. It also doesn’t require any interruption of the circuit, so you can keep your electronics running during testing. Since we have the multimeter set to a high 200 volts, it shows “1.6” on the screen, meaning 1.6 volts. The black probe will go into the third jack, labeled “COM.” The red probe plugs into the fourth jack. For starters, lets go over some of the different parts of a multimeter. It should clearly read the values that you’re trying to measure. If you’re measuring a low-current fuse or a small battery, you might have to switch the dial to a lower range to get an accurate reading. Generally, a battery produces DC voltage (like your car or flashlight) and your home’s electrical service is AC voltage. AC voltage has a symbol that looks like a sine wave, which is the universal symbol for AC. Likewise, electrical potential is the amount of force in a circuit available to push the electrical current if allowed to flow. Here, you can see that we have a more accurate reading that hovers between 1.60 and 1.61 volts. After you have recorded your reading, turn off the multimeter to preserve the batteries. Think of water flowing through a garden hose. Since we launched in 2006, our articles have been read more than 1 billion times. I’m glad I could be helpful. Here are the 2 simple steps to determine watts: The only way to master this is to get out there and start doing it! In our case, we’ll be simplifying things quite a bit and will just use a copper wire, but you can pretend that there’s a complex circuit in between the two ends, or that the wire is an audio cable and you want to make sure it’s working fine. How to Use a Multimeter. Turn off the power to the circuit that you’ll be measuring. In a more practical situation, you could do this type of measuring on a car battery to see if it might be dying or if the alternator (which is what charges the battery) is going bad. An object or appliance’s resistance to electric current is measured in ohms and its symbol is the Greek capital letter, omega  (Ω). The AstroAI Digital Multimeter, TRMS 4000 Counts Volt Meter is a product I would seriously recommend. Before you will test alternator with multmeter, ensure your car battery is completely charged. This is because the probes can actually charge the capacitor slightly. There’s a lot going on when you look at the selection knob on a multimeter, but if you’re only going to be doing some basic stuff, you won’t even use half of all the settings. However, if it were to read 1.2 volts, it’s close to being unusable. If the alternator produces too little voltage, it will not be charging the battery properly. He has certifications in automation and control technology. Using a voltmeter is one of the most practical and most accurate ways you can determine the condition of your car’s alternator. Set your multimeter to the continuity setting using the selection knob. Get information on Electrician programs by entering your zip code and request enrollment information. Vehicle 2 solid 15.3. Almost every voltmeter or multimeter uses a large dial to set the mode. More often, it will be on the order of 0.5 milliamps. Your multimeter might have completely separate ports for measuring amps, while the other port is specifically just for voltage, resistance, and continuity, but most cheaper multimeters will share ports. Identify whether the voltage you’re measuring is AC or DC. Here are the steps you take to measure current with your multimeter: 1. Join 350,000 subscribers and get a daily digest of news, geek trivia, and our feature articles. This would be correct since we haven’t connected the probes to anything yet. , so I bought one but know absolutely nothIng about a multimeter and am “scared to (death) of electricity. Using a digital multimeter for testing the charging system for your car needs some technique. You can use the resistance setting of the meter to check for problems with high-tension leads. An alternator goes dead and the car will run on the battery alone until the battery goes dead, then the car quits running. Check the resistance of fuses in your car or appliances. How to Use a Voltmeter: Find Your Setting Set the Dial. Notify me of follow-up comments by email. Now, let’s test the continuity of a circuit. The symbols around the dial might look foreign to you, but don’t worry. We’re going to start out with the basics of how to use and read a multimeter. Results = Bad alt and Good batt Take multi meter to vehicles. Likewise, no electrical conductor is perfect. Fully charged batteries should measure at 12.6 volts or above. The hose is now under pressure, isn’t it? As you drive along the belt driven alternator takes over the role of delivering power to the car's electrical systems and also recharges the battery. Multimeters measure AC and DC voltage, electrical resistance, and the flow of current. Each setting may also have different number values, which are there to measure different strengths of voltages, resistances, and amps. In a more practical situation, you could do this type of measuring on a car battery to see if it might be dying or if the alternator (which is what charges the battery) is going bad. Finally, turn the selection switch back to the highest resistance units. The gauge is comparing the pressure inside the hose with the atmosphere outside and telling you the difference in psi. To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. If you’re doing any kind of electrical work—no matter what the application is—one of the best tools you can have at your disposal is a multimeter. Here are some additional tips to make sure you are taking a correct resistance measurement: A multimeter does not directly measure power or watts. Gloves are always a good idea when working with electricity. You’ll see what we mean. That’s good! Always start at the highest voltage range on your multimeter selection switch. Let’s check your car battery with a multimeter: Now let’s check your alternator with a multimeter: Basics of Electricity and Electrical Units, How to Use and Read a Multimeter to Measure Voltage, How to Measure Current with a Clamp Meter, how to measure current with a clamp meter. Turn the selector dial to A which is current. Above is a crude mockup of what this would look like with a basic clock running off of a AA battery. Anyway, your multimeter, correctly used, can help you diagnose and repair many of these troubles. You can get something basic like this $8 model, which comes with everything you would need. millionths of amps. A reading between 12.4-12.7 volts means that the battery is in good shape. Troubleshoot any electrical problems in your home, car, or personal devices. Before you learn how to test a car battery, there are a couple of things to keep in mind. A resistor is often the whole point of having an electrical circuit in the first place. It could be that there is too much load on that circuit. How to Measure Resistance10. OK let’s get real. Otherwise you could blow the fuse that’s inside of the multimeter. This jack should be marked with an, The second red probe jack (outlet #2) is for current measurements between 0 and 400 mA, or for the frequency of this low current. If you need to see whether or not an outlet is working, use a non-contact tester instead. Now, just so you don’t get confused, your multimeter may have any number of additional buttons on the face. You can also use it to test old batteries, extension cords, and light bulbs without plugging them in. Plug the red probe into the jack, marked with a, Turn your selector switch to the highest setting in the proper voltage category. Always ensure that the multimeter is rated for the voltage of the system you plan to test. On the face of your multimeter, you’ll find the settings. Fuses and breakers are designed to open the circuit If they sense that too much current is flowing through that circuit. Detecting magnetic induction is safer for the meter itself, and clamp multimeters can be used for much higher currents than a multimeter with probes. Warning: Always turn off the power to the area your reading whenever you use the ohms feature. Use a multimeter in your HVAC unit to make sure the compressor is getting the right amount of electrical power. Important Safety Advice3. Or, the circuit breaker could simply be doing its job. How to Measure Current with a Clamp Meter9. Get ready! Reply Note that the multimeter listed below should be able to measure the same amperage of the fuses, up to 20 amps, and as low as the hundredths range. Multimeter Basics2. Is it just running out the end from gravity, or is it being pushed? Make sure you are clamping on to only one wire at a time. You can also test that the continuity feature works on your multimeter by touching both probes to each other. If you are measuring particularly high resistance and your fingers are in contact with the terminals, it’s possible that your fingers will affect the resistance reading. However, it is not the only test available for you. Instead, an appliance’s watts can be calculated rather simply by measuring the voltage and the current, and then multiplying them together. Capacitors may take a moment to stabilize when you apply the multimeter probes. How to Search for YouTube Videos by Hashtag, How to Use the TRIM Function in Microsoft Excel, How to Transfer LastPass Passwords to 1Password, How to Use Two HomePods as a Stereo Pair With the Apple TV, How to Automatically Delete Old Text Messages on iPhone or iPad, © 2021 LifeSavvy Media. It’s also known as the return terminal. The above article may contain affiliate links, which help support How-To Geek. How to Check Your Car Battery with a Multimeter. Always use a digital multimeter with a minimum 10 megaohms of impedance, to prevent damage to sensitive electronic and electrical devices in your vehicle. When the engine is running, this measurement should be 13.7 to 14.7 volts. A reading between 12.4-12.7 volts means that the battery is in good shape. Hybrid vehicles use a high voltage (140 to 300 volt) battery, generator and electrical motor for their stop-start systems and electric drive. Copyright Text 2016-2021 by asktheelectricalguy.com, We use cookies on this site to optimize site functionality and give you the best possible experience. Yours might be slightly different in some ways, but all multimeters are similar for the most part. The greater the force, the higher the voltage. We call it a clamping amp meter. For testing a fuse, you can either use it to measure the continuity (which tests if the circuit is complete) or the ohms (which tests resistance). Next, make sure the circuit is unplugged and has no power. 2. Every component in your vehicle uses DC volts for power, and most electrical diagnostics in a car involve the power circuit. How-To Geek is where you turn when you want experts to explain technology.

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