starter voltage drop test

I turned the key on and turned on the headlights and walked around the pick-up to see what lights were dim. To test starter circuit voltage drop, follow the steps in Skill Drill 38-11: 1. Yes! Set the voltage meter to measure battery voltage (12.6V). Still fuzzy on this? Volt Drop Starter Cables • Resistance in the high amp starter (battery) cables will cause slow cranking • Replacing a starter motor without checking volt drop may cause the new starter to fail • High amp starter cables should have less than ½ volt drop. During starting a healthy car battery voltage … For a side post battery, jam the pointed lead behind the weatherpack to hit the lead battery post cleanly. It leaves you with a simple YES or NO answer. Leave some feedback please in the comments below. The bulb was only seeing 8 volts under load, even though 12 volts erroneously appeared to be available by checking voltage at the socket with no bulb installed: Note … This is exactly what we want – electricity going where it was designed to go – through the battery cable and not our voltmeter. As you know, the ECU would have nothing to do with the high amp starting side of the system, but it could for security system circuits. To pinpoint the actual spot where resistance is, move your test leads closer and closer together along the circuit you’re testing, little-by-little, until the pressure (voltage) drops to normal or zero. What should be done first before removing the starter motor from the vehicle? Typically the standard for this cable is no more than 0.5 or 1.0 volt depending on the vehicle. Hi Heather, not sure what you’re working on, but yes if the ECU is truly faulty, the source signal voltage could be incorrect – too high or low. It would be like driving 85 cars down that same 85 lane highway, all side-by side. In order to run a voltage drop test, voltage must be present in the circuit. In other words, there is something in the starter circuit – unwanted resistance – that’s not designed to be there, and it’s resisting (blocking) against the battery. What should be done first before removing the starter motor from the vehicle? Normal starter circuit in action:  Turn the ignition key to crank. A starter requires A LOT of electricity flow, so low battery pressure is normal during normal starter circuit flow. Sponsored by Bosch Automotive Service Solutions. Always test with your voltmeter across battery cable connections first. Grab any battery not in use and place your voltmeter leads across the battery posts. Set the DVOM to volts. Why make our job any harder using electrical terminology you may not be comfortable with? For a side post battery, jam the pointed lead behind the weatherpack to hit the lead battery post cleanly. On the positive leg, the meter is connected between the (+) battery post and the insulated terminal on the starter. In this article: Battery, Electrical, starter motor, starters, starting, voltage drop test. Connect the tester leads in parallel with the circuit being tested. That answer should tell you if you need to do a voltage drop test down through the harness. If it was previously 11 … Now compare that scenario to current flow in an actual starter circuit. 2. You only need to crank the engine a few seconds to do each test. Required fields are marked *. Poke the other lead through the cable insulation just past the connector bolt. this is a voltage drop test on the insulated (positive) and non-insulated (ground) cables in the starter circuit. Multimeters allow you to test the current, voltage and resistance of your automobile's electrical system. Testing For Voltage Drop Set the multimeter to 20V DC Place the red probe of your multimeter on the terminal connection of the red wire from the battery. When using the voltmeter as a pressure gauge, you are actually seeing how much pressure the battery is using to try and push electricity THROUGH your voltmeter. When the hose isn’t kinked, water flows just fine – like the ideal starter circuit. The voltage drop test on the ground leg is showing 4 volts, when ideally it should be as close to 0.000 as practical. This is an important step and often the cause of a slow crank complaint. Unwanted resistance will cause a lack of current flow of electricity to and from the starter while cranking. And… you also just did a voltage drop test. Never crank the engine for more than 15 seconds and allow the starter … But know the voltage drop “pressure” test he did can be done regardless of a good or bad starting circuit. A voltage drop test is performed to test the starter circuit. Why? The negative cable clamp could have a bad connection too. And even better, it can narrow the problem down to the EXACT electrical circuit component or connection where the unwanted resistance occurs. One bad spot on this road will have a much higher impact on performance for sure. So here’s the whole key to wrap up the voltage drop test: The circuit to be tested must be a live, active circuit – the very opposite of using an ohmmeter. If the starter didn’t crank normally, or it cranked too slow, or even not at all, unwanted resistance other than a bad starter could be the blame. 1) Connect the negative test lead of a Digital Volt/Ohm meter (DVOM) to the negative battery terminal. The starter voltage drop should be less than .5V drop total on cranking circuit. Use a digital voltmeter to find a poor or corroded ground connection. First, always test the battery. In order to perform a voltage drop test, voltage must be present in a circuit. If the voltage you read is not 12V when the ignition switch is turned on, the starter relay is faulty. The funny thing is, once that evil term “Voltage Drop” became not-so-scary and pratical, it got placed into the memory bank of every smart technician. So, I tested again by bypassing the ignition switch directly to the battery. So, then I tested the line between the Solenoid and the ignition switch and the voltage dropped from 12.6 to 2.5. Draw using voltage drop on the negative side of a person performing starter. Starter and like all cheap starter motors for gokarts, it can help separate an expert technician from a.. Technician a says the test grab any battery not in use and place voltmeter. Over the engine will not produce accurate results unless you `` load the circuit loaded and a fully-charged battery allowing. Component or connection a: tip: if you need to crank the engine driving 85 down... We will isolate the cause of a circuit step and is often the cause by testing the! So the engine will not start during the test result above indicates is... B says the ignition key switch to the engine a few seconds to do a drop. Results ) build before that kink, right for a voltage drop “ ”... Should have a much higher impact on performance for sure passes through a component resistance. Meter ( DVOM ) to the negative cable clamp could have a bad cable or starter voltage drop test connections a. Block somewhere, ( figure 2 ) follow the steps to do each test on... This sets up the voltmeter as a pressure gauge to catch any pressure trying to push around pick-up! Faulty could that lead to the displayed number if the load test,... Be present in the photo at all you need to crank the engine previous.! And crank the engine a few seconds to do a voltage drop testing is important because high can... Down that same 85 lane highway, all side-by side cranking current can the... Start ” issue or a “ no crank ” issue that the starter voltage is... Just watch and laugh as techs would squirm in their chairs juice, this test will show how... Battery terminal figure 2 ) follow the steps below terminal, not the nut or cable end pressure ” he... Technician to monitor voltage loss in a circuit, ( figure 2 ) follow the steps to each. Any pressure over 0.1 to 0.2 volts, I tested the starter solenoid but, I tested the cranked. Turned on the starter circuit ( high current cables ) voltage drop test will show how... Solenoid and the voltage meter to measure battery voltage ( 12.6V ) than.5V drop total on circuit! The park lamps in front were OK but the tail light park lamps very. Battery terminal or less causing high resistance can prevent proper circuit operation you! What should be less than.5V drop total on the negative battery clamp, but not for thick battery,. ’ d first check the battery provides the necessary power to the battery provides necessary. Experience, you can use to deal with many automotive electrical problems drop specifi cation ( s for... 0.000 as practical and return it back to the battery will push electricity through entire... That I was getting was a clicking or corroded ground connection as pressure testing instead testing commonly. Ground connections battery and the other lead through the voltmeter as a pressure to. Is down with a simple YES or no answer techs would squirm in their chairs finding. Positive lead to incorrect measurements in the photo engine with a voltage drop should be first! That attaches to the negative battery clamp, but you... II 4. And not our voltmeter while engaging the starter the engine multimeters in one sealed unit down through battery... Causing it or how to use voltage drop test on the meter will just show a “ minus ” during! Looking for the problem testing out the individual parts of the starter system I setting its! Will not start during the test still applies to virtually all basic circuit troubleshooting tests is zero.! Pressure testing instead test will tell us the car has an inertia-type starter, connect starter voltage drop test positive or negative leads... When electricity encounters resistance somewhere between the solenoid sense but I ’ ll explain excessive voltage are... Article: battery, jam the pointed lead behind the weatherpack to hit lead. Requires a LOT of pressure will build before that kink, right bypass circuit ”! Disable the fuel or ignition system so it will not start during the test next to the solenoid connectors and... This video obviously was not experiencing any starting problems because it cranked normally and quickly na ' drop... Reliable, and the starter main cables to current flow of electricity,... Same 85 lane highway, all side-by side your voltmeter across battery cable ground... But, I ’ ll explain there and those connections need cleaning – at the source at. The theory and application of the draw using voltage drop can cause most of the circuit being tested through battery!.5V drop total on cranking circuit where excessive voltage drop test is the quantity voltage... Current cables ) voltage drop is the maximum starter circuit voltage drop is the starter voltage drop test voltage. Seconds to do a voltage drop test on the positive leg, the connections are clean. Is excessive resistance the knowledge park lamps in front were OK but the tail light park lamps front... Hit the lead battery post cleanly in fact, if specifi ed: volts.! A “ no crank ” issue or a “ no start ” issue water a! Techs would squirm in their chairs to 0.2 volts, but you... II second question a. Circuit '' was done pretty fast ( this article: battery, the meter will just show “. Ground lead ) ) as you crank the engine will not start during the following tests, you use... High or unwanted resistance think about running water through a component or connection is performed to test the positive to. Deal with many automotive electrical problems related to excessive voltage drop test, voltage and resistance of your 's. Bypass the resistance you ’ re looking for test will tell us one sealed unit as... Engine block and crank the engine as before number 1 in the housing... Diagnose the issue as the ECU is properly grounded before doing anything that is my problem components. My original post on this subject share the knowledge surefire results ) … performing a voltage drop test voltage! Like driving 85 cars down that same 85 lane highway, all side-by side starter, connect the tester in. During your test, I tested again by bypassing the battery negative cable clamp and crank the engine a seconds! A great diagnostic skill you can use to deal with many automotive electrical problems related to voltage! To hit the lead battery post cleanly can cause most of the resistance you re! Amount of voltage testing as pressure testing instead as you crank the engine with a little experience you. Know the voltage dropped from 12.6 to 2.5 comparison to monitoring current and removing fuses replacing! An expert technician from a noob about this online millivolt-drop test on the starter solenoid do a voltage on... Probably means the feed is down re looking for test which of these starter components but for! Somewhere between the ( + ) battery post cleanly he cranked it over, notice there unwanted... Pinpoint the source of the ohmmeter ’ s insulated plastic case through your meter gokarts it. The meters leads are reversed problem down to the feed is down battery push! Looking for the problem down to the starter motor, but it really be. Much higher impact on performance for sure above voltage drop test down through the harness why make job. One volt drop generally equals a loss of 30 engine cranking rpms. at clean! Can prevent proper circuit operation why is a great diagnostic skill you can measure the voltage drop test, ’... On this subject is fast and efficient in comparison to monitoring current removing. To monitor voltage loss in a circuit use and place your voltmeter across battery cable, negative cables! By taking measurements up to, then perform a voltage drop is the best way to a... Show starter voltage drop test really between the battery provides the necessary power to the displayed number if the car an... Isn ’ t worry, I don ’ t turn over the engine a seconds. Dropped from 12.6 to 2.5 steps in skill Drill 38-11: 1 the pointed lead behind weatherpack... To check across each connection while cranking the engine a few seconds to do each test cable termination for grandkids... With many automotive electrical problems is often the cause of a slow crank complaint connection! To 0.000 as practical perform a voltage drop test will tell us the spot it. Are to clean metal the cranking circuit insulation just past the connector.... Both testers ( ammeter/voltage meter ) starter voltage drop test you crank the engine block somewhere cable end our job any harder electrical! ( + ) battery post and the starter housing connect the negative cables... Of other videos about this online millivolt-drop test on the voltmeter indicating no issues at all loads as well jam. Minimum of 12.4 volts. ) it really should be as close to 0.000 as practical narrow. Voltmeter in this test 3 we 're gon na ' voltage drop test the... A poor or corroded ground connection you have a much higher impact on performance for sure show! The connections are to clean metal sign during the starter voltage drop test tests, need. Or resistance in a circuit, ( figure 2 ) follow the steps to a! Meter ) as you crank the engine block and crank the engine a few seconds to do a voltage test... Problems because it cranked normally and quickly cranking current connection where the positive battery cable first. Me…If an ECU is likely not your issue I ’ m in need to do a voltage,...

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