The closer to the source of the noise the alternator the more accurate a measurement youll get. Alternator problems manifest themselves in various ways, depending upon the particular failure. How to perform a compression test with a scope verusvantage. The older alternators had the diodes pressed in top hat and seemed to be very reliable. On many batteryless test benches, ripple voltage for good alternators may be as high as three or four volts.
The quick ripple tester is designed to easily and efficiently test alternators for a variety of issues, including ripple, through the dc outlet cigarette lighter. Not all scopes have the capability of ac input coupling, this makes it difficult to troubleshoot alternator ripple and other signals. Alternator troubleshooting with an oscilloscope bright. You do not need a scope with sample rate above 300mhz. Do you know what excessive ripple means when associated. It would be nice to have a selection for an ac coupled 1 or 2 volt range like that displayed during the alternator test. When the engine is off, the battery powers the lights and accessories. Go in there and heres how i hook it up, heres what its supposed to look like. With other scopes you need to enable ac input coupling. Aug 01, 2018 a basic overview of how to test an alternator using the ac ripple test method. If it is bad, is the replacement as involved as the service manual suggests removal of. Sep 06, 2009 bad diodes reduce alternator output 33%, 67%, or 100%, depending on how many go bad, and the ripple can drive electronics crazy. You see, wishing for success doesnt match using proven procedures such as a thorough battery analysis, a proper alternator output test, a scope check and.
The display should change to indicate the measured value of the ripple voltage amplitude. Allowable ac ripple current at the alternator battery post was created by sailorbob in haldermans book, automotive electrical and engine performance, 7th ed. Oscilloscope analysis of alternator all about circuits. Updating your ripple voltage tutorial vensel enterprises. With an interro pda, select the diode pattern test in the engine test menu and connect the current probe to either battery cable and record the ripple pattern. Interesting alternator ripple snapon diagnostics product forums. The least expensive multimeter will show this characteristic on a diode and a cheap digital multimeter will have a settin. Leaky diodes will generate ac ripples along your electrical system. Go to the dropdown menu bar at the lower left corner of the waveform library window and select alternator ac ripple diode test. Alternator whine can be a symptom of a bad alternator diode. Alternator ripple too big and battery keeps running flat.
Ripple factor can be defined as the ratio of the root mean square rms value of the ripple voltage to the absolute value of the dc component of the output voltage. If so, all the basic bench tests are the same as for a 12 volt alternator. Now the alternator produces power in three phases so take 2 more sets of waves and over lay them on your first set but offset them equally. Quick ripple altenator tester automotive car care tools and. We test industrial battery systems for the ripple current output from the chargers as a way of measuring the performance of the chargers. Alternator troubleshooting with an oscilloscope bright hub. There is a hand held unit with a probe that clamps over the alternator output wire.
The increased electronics content of modern automobiles has made battery performance fundamental to overall vehicle performance in many areas. Since an alternator mechanism involves complicated stages of electrical and electronic networks, accurate readings of the various hidden snags can only be done by analyzing the different waveform curves generated over an oscilloscope screen. A car alternator is a dc system, the voltage is around 14vdc when charging with some audio frequency ac ripple due to the rectification of the alternator output. Diy alternator test using the ac ripple method youtube. Control module voltage at 17v, but battery and alt are. The shop that is saying the alternator is testing the alternator with a dc voltmeter. Alternator troubleshooting with an oscilloscope is probably the only best possible way of doing it. Please watch the following video below to watch the test being performed by. Allowable ac ripple current at the alternator battery post. Alternator ripple testing was doing an ac ripple test on a 2002 chev avalanche, 5. Inside alternator ectromagnetic field that has wire coils on each sides collects spinning motion. If they have a bad alternator or its putting out some sort of weird pattern, its going to screw up all your diagnostics, so its a. Some parts shops have the ability to do an off vehicle alternator test. This should be one of the first things you might want to do if you suspect you have an electrical problem in a car.
Dynamic testing is fairly straight forward and is the same as 12 volt alternators except all the voltages are doubled. When the engine is running, an alternator generates electrical energy to supply the vehicles onboard electrical systems and replace the battery charge consumed during cranking. One of the more powerful features inside the guided component tests and all of our lab scope products is this thing called a top level menu. On a scope with the correct filter or leads, ripple voltage looks at the alternating current from a diode. A ripple test showed that the alternator should be replaced. Send us a message and we will put you on a notification list. The alternator ripple test is designed primarily to verify the proper operation of the rectifier diodes by monitoring the current waveform for the characteristics of a bad diode or open phase winding. Alternator ripple testing snapon diagnostics product forums. Any simple diode will exhibit a fronttoback ratio since they are designed to allow current to flow in only one direction. How about using cursors in the scope and measuring using that. Just about any scope would be good enough for this. Windings are wrapped around a soft, laminated iron core or ring. Sep 30, 2012 a car alternator is a dc system, the voltage is around 14vdc when charging with some audio frequency ac ripple due to the rectification of the alternator output.
How do you check ripple voltage in an alternator answers. Ac ripple current there is always an ac component in the dc output from our alternating current generators alternators the diodes imperfectly clip the ac output of the alternator and convert it to dc. Then i can look at the ripple coming off of the rectifier assembly, and if i get an event thats occurring at exactly the. Repair or replace, a good alternator should not produce more than 10% what may result if you disconnect the battery cable with the engine running. Without the benefit of a battery, other forms of filters typically capacitors must be used to reduce not only the alternator ripple voltage, but also the 60 hz line ripple in the simulated battery. Jan 26, 2019 alternator problems manifest themselves in various ways, depending upon the particular failure.
All of the previous alternator tests showed around 12v loaded or not loaded. You will see that picoscope has displayed an example waveform and is. To test for this condition switch the voltmeter to ac voltage with the engine at about 1200 rpm, the meter should read 0 volts. The voltage should remain high with these circuits on. Test alternator by connecting voltmeter on dc 20, red on positive battery terminal and black on negative battery terminal. Further guidance when the engine is running, an alternator generates electrical energy to supply the vehicles onboard electrical systems and replace the battery charge consumed during cranking. Failed load test alternator ripple is electrical noise that is produced during the rectification of the. One click on a button on the page describing how to measure on a specific component launches the measurement software and loads the preferred measurement settings for that. Without the benefit of a battery, other forms of filters typically capacitors must be used to reduce not only the alternator ripple voltage, but also the 60 hz. In order to characterize a ripple voltage completely, the frequency needs to be measured. The pattern looks like something you get when your scope isnt grounded properly. It does the job for you by filtering out the dc steady portion of the signal so you can concentrate on the ac always changing signal, making it easy work to. The multimeter will only measure the ac component of the signal i. Today were going to talk about an alternator ripple test.
As in the picture alternator 1 the test lead was grounded and connected to terminal marked w. The stator produces electrical output of the alternator. When its time for a diagnostic showdown and youre forced to draw your scope, you dont. Suppose i could just put a cap in line like i do for my scope, but my. My ripple test post regulator replacement picture has big spikes. The only thing that i dont care for is that you cannot record the alternator ripple waveform. At the frequency that this ripple occurs, the dc voltmeter will not pick it up, but the alternator will have an adequate dc voltage level to look good to them. The battery is the heart of the system that produces voltage and provides storage for electrical current. Automotive batteries have been with us for a long time now, so most of us havent stopped to revisit the technology behind them in a good while. If they have a bad alternator or its putting out some sort of weird pattern, its going to screw up all your diagnostics, so its a good place to start. A basic overview of how to test an alternator using the ac ripple test method.
Alternator ripple test diagnostic quick tips snapon training solutions. I put a piece of reflective tape on the pulley thats on the alternator shaft, and i have an optical tach sensor that i use to provide a trigger signal for the scope. Two test methods can be used to test the alternator without disassembly. Alternator whine in stereo on 85 eldo, ripple voltage. If you are thinking that a running alternator testing may be easily done using a digital multimeter, you are terribly mistaken. Alternator ripple test diagnostic quick tips snapon training. May 03, 2020 test alternator by connecting voltmeter on dc 20, red on positive battery terminal and black on negative battery terminal. The subject was a 60a nippondenso from a civic, running at the equivalent of fast idle. A good battery acts like a big capacitor and usually filters out unwanted ac ripple. Since an alternator mechanism involves complicated stages of electrical and electronic networks, accurate readings of the various hidden snags can only be done by. Go to the dropdown menu bar at the lower left corner of the waveform library window and select, alternator ac ripple diode test. The scope is the same one i used on the accord also connected to the battery. The new alternator had a ripple test reading of 55mv, which was acceptable. If you have a bad diode and remove the battery lead for an oldfashioned alternator test the ripple can reach most of a hundred volts and ruin thousands of dollars worth of computers, controllers, sound system and.
You need to do a ac ripple test with a scope to properly see if the diode is bad. Control module voltage at 17v, but battery and alt are reading 14. For the full version of this video and much more diagnostic and training videos please visit my new website. I checked from the alternator post to the battery ground. The waveform selector only records on a 3v to 15v scale so any ripple in the 50 to 200 mv range is invisible. A unique feature of atis is the direct coupling to the automotive test scope ats64dxmsg, automotive test scope ats605004dxms and automotive test scope ats5004d. If you are getting ac readings of 25 volts it kind of points towards a bad battery or battery connection and possibly a bad diode. Stress test the alternator place a load on the alternator by turning on the headlights, the radio and the air conditioning. The alternator may not be providing enough current to keep the battery charged,or it maybe it will. The next group of ripple tests occurred on an alternator test machine equipped with a conventional car battery. A single channel, pocketsized, digital storage oscilloscope thats small, quick, and powerful. When ac noise is detected on a dc signal, test the alternator ripple. Initial evaluation by monitoring voltage ripple can be misleading. Airfuel ratio sensor test fuel injector voltage and current tests scope alternator ripple test scope fuel pump current ramp test scope bmw rain sensor calibration harleydavidson abs brake bleed can bus diagnostics scope harleydavidson functional tests chevrolet volt coolant pump bleed harleydavidson key fob programming.
Bad diodes reduce alternator output 33%, 67%, or 100%, depending on how many go bad, and the ripple can drive electronics crazy. An alternator is producing % of its rated amperage output in ac ripple amperes, whats the next step. Start vehicle, and voltage on voltmeter should increase to around volts and stabilize there. If voltage is present one or more diodes has failed and the alternator should be replaced.
If an alternator diode fails, the amount of ripple voltage increases markedly. Bring the probes into contact with the circuit that has the ripple voltage. This kit includes the most common accessories needed for labscope diagnostics. For the full version of this video and much more diagnostic and. So i did a ripple test and found a rather strange looking pattern on the scope. A the battery, c alternator and c voltage regulator. Then i can look at the ripple coming off of the rectifier assembly, and if. The early chrysler alternator had brushes at right angles which was nice. Heres how were going measure using the cursors in there. Allows the user to test an alternator for bad diodes, bad stators, and intermittent diodes or stators without ever lifting the hood.
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