In order to get maximum battery life proper charging voltage must be maintained. It will self-excite, meaning that it can start charging and stop charging all on its own. The yellow/white wire is the voltage sense and power for the field. 5 Montana at about 3,500 rpm the battery light comes on and battery stops charging when on tickover the battery measures 14. 3v at idle but above that at around 2k and up it would act normal aka why pepboys thinks its good. 6 volts -installed back into car not putting out voltage - checked the voltages with multimeter still no good - replaced the plug going. For short periods of time, this works-but is not ideal, thus the drawback of a 1-wire on a vehicle that. A while back on the forum the view became that the charge light was not necessary for a Bosch 85 amp Alternator because they can self excite. The mechanic tested the new alternator while it was acting up and the tester showed it was not charging correctly. If you're not sure what the alternator shaft speed is, you can determine. , connecting the alternator to the battery. A generator, however, can be used for charging a dead battery. Powermaster uses a state-of-the-art computer alternator dyno to. A check showed the Charge light wasn't coming on which meant no excitation for the Rotor. If the alternators set point was 14. Evidently the alternator was severely over loaded to a point where it was not able to keep up with the demand. When the engine spins the alternator around, the alternator induces an AC voltage that is converted to DC and used to charge the car's electrical system. Oct 17, 2013 · This video explains one of the solutions as to why you might be experiencing a charge issue on your duramax. An alternator malfunction can have different causes. Engine RPM and battery charging. I checked the rectifier diodes. Oct 24, 2018 · The alternator and charging system problems are not just the problems in itself, but they also cause a number of problems to your vehicle. This output voltage must not be too high. Feb 28, 2005 · Presumably the figure in the spec for the alternator assumes a certain rpm (which wasn't listed in my Haynes manual). 67V and this does not even consider any voltage drop in the system wiring between the back of the alternator and the battery bank. 5v prior to starting the engine. Start the engine and put it at high idle (around 1100 RPM). The other day while digging the alternator light came on and my tachometer stopped working. The alternator was replaced 3 times before the vehicle was diagnosed properly. The alternator failed not long after that with no continuity between the slip rings, so it may have been the winding on it's way out. I have a manual and did some checking. Nov 17, 2009 · It will be the alternator that is the problem,the gauge would show charging but the battery light would come on if it was just the battery,most likely the problem. If a magnetic field is present. Also, measure the voltage between the battery positive post and the. Because a car’s crankshaft generally operates at around 1,000-4,000 rpm, a car’s alternator is designed to put out good charging voltage and amperage around 3,000-12,000 RPM. The company has built professional alternator/starter test machines for nearly 40 years. 50, which means that the fuel pump starts to lose fuel, according to the tuner he said it can't drop lower than 13. Because the high-revving 289 Hi-Po does its best work at high RPM, total timing is completely in by 5,000 rpm, with peak horsepower and torque at 6,000 rpm. Oct 03, 2012 · That seems a little high, so I put the meter on it and got reading of 15. I do not need high charge curent. If the rpms drop below the alternator's cut-in speed, the alternator will quit charging until the rpms are increased. Increase and hold engine speed to 2000 rpm. Idle is about 650rpm. Nov 11, 2019 · The good news is that replacing a factory alternator with a high output alternator, in and of itself, isn’t going to damage the rest of the electronics in your car, even if the new alternator is much, much bigger than the old one. Alternator not charging at high rpm on 87 Volvo 740 I install a new a alternator but is not charging at higthrpm - Volvo 1987 740 question. Not sure if anyone here is still interested but, UPDATE. It is just a hobby to keep me motivated doing sport indoor. It would take a hurricane force wind to turn a small wind turbine fast enough to even start charging a battery. Low Rpm Permanent Magnet Generator, Brushless Direct Drive Generator, Low Speed 3 Phase Alternator manufacturer / supplier in China, offering 25kw Low Rpm High Efficiency Permanent Magnet Generator for Sale, 10kw Low Speed Permanent Magnetic Generator, Low Rpm Permanent Magnet Generator 1kw - 5000kw and so on. I don't want to get a new alternator if mine is not bad. Designed to fit stock brackets, this Mean Green unit is a direct bolt-in. and alternator, and between alternator and battery. I did not buy the H. Increase and hold engine speed to 2000 rpm. this makes high ac voltage, witch then runs to the voltage regulator/rectifier witch drops it to 14v dc, if this unit is but you wont charge the battery or over charge it and kill the battery. Smaller aux batteries are unlikely to overload the alternator: maximum wet battery size = (60-6)/0. If charging system can operate ALL electrical loads AND Maintain 13. A while back on the forum the view became that the charge light was not necessary for a Bosch 85 amp Alternator because they can self excite. When Innotec discusses DC Generator heads, we are really saying a 3 phase Permanent Magnet Alternator coupled with either an internal or external rectifier/charge controller. except this time its only at lower rpm while driving. If the excitation current is not present at all, the alternator will never charge. Nov 21, 2014 · Charging AGM batteries from car alternator. It is load related. This can especially be true with a high amp alt that needs greater field voltage and has less idle charging output. To reach maximum alternator rpm, a normal automotive engine application would have to be turning 8,000 rpm, which would not happen for long!. The new alternator did the exact same thing. I have one on a JD 60 which has a max rpm of 1050 and it works fine. 8 Volts at the alternator and battery terminals when the engine is at idle. Not looking for an argument. As soon as I hit the gas, or even tap it it works fine. 67V and this does not even consider any voltage drop in the system wiring between the back of the alternator and the battery bank. 7 liter volvo penta 1982, with a paris rhone 50 amp alternator builr in regulator, is this normal??. If yes to the light on the dash at key on, I would inspect the alternator charging wire from alternator to battery. If the alternator is not receiving power from the ignition switch then it isn't going to generate power. The other day, on the way home from last minute christmas shopping my truck went dead well not dead, but the headlights shut off, dash shut off, and the "service battery charging system" displayed on my DIC. (The idling rpm is not abnormally low). At 1000 rpm, yes, but, not 800 rpm. 5V @ 2,000 RPM = Under-Charging Test for Undercharging. if I am not mistake this sounds the opposite of that isn't the floating brushes a flickering alternator light at high rpm? The high rotational speed of the alternator would cause the brushes to float not low rpm. Fully charge your battery with a charger (you can't reliably test a discharged battery) and have it load tested at the parts store. If your alternator tests good, the problem is not a bad alternator but something else. you cannot run a car without the battery, it is a very important part of the charge system, The alternator monitors the battery voltage and adjust acordingly, Without the battery the is no battery sense and the alternator will overcharge, possibly damaging electronics within the vehicle, this is why it is not a good idea to disconnect the battery while the engine is runningand also Without a. I indicated that by the time before I removed the alternator, the Battery not Charging message was on solid. My alternator (and tachometer) does not kick in until I apply high revs (3500 rpm). Therefore, Powermaster does not recommend power pulleys with high amp alternators. A voltage in excess of standard charging voltage - 13. Regulated system output will vary based on the battery state of charge. Never had this kind of thing happen. A one wire alternator is used where you do not want to have any connection from a vehicle to operate an alternator. All we do is Alternators. and alternator, and between alternator and battery. Be careful with a smaller pulley. By design, not tested. Our alternators are self exciting after 2000+rpms so there must be an issue thats not triggering the alternator at start up. Sep 27, 2018 · The seller agreed and brought it to his mechanic which replaced the alternator and to everyone's surprise, the new one wasn't charging either! Long story short, the seller's mechanic discovered that if you increase the throttle a bit, the alternator jumps to 14. 170 amp S series and 250 amp Elite series units are the best choice for high RPM racing applications. Re: Alternator not charging battery at high rpms « Reply #5 on: 19 October 2016, 04:58 PM » To expand on Harv's comments; instead of buying another alternator not to mention the remove and replace of the alternator, consider replacing the voltage regulator set which comes with brushes if I recall correctly. The battery was good, the voltage regulator was good. The ignition power wire to the alternator will be purple. and fixed all my issues! Good charging even at high RPM, and shifting is back to normal at high RPM's. Hey, The 3 wire internally regulated alternator does not charge the battery when at low RPM. Always connect these terminals hroug almp. Therefore, Powermaster does not recommend power pulleys with high amp alternators. Increase and hold engine speed to 2000 rpm. I have heavy 4 gauge with inline fuse to alternator from battery also kept the factory wiring hookup as well mine charges at 700 RPM 14. If charging system can operate ALL electrical loads AND Maintain 13. The diagnostics are really easy. The maximum output demand for the ASX-200 alternator should not exceed 50 amps. first if the alternator stopped charging would that also effect the ac pulse. The cause is not always due to an internal alternator fault, such as a faulty winding, rotor, rectifier or control unit. I may be making a big deal about something not so critical: the "speed" (rpm's) at which you drive the alternator. A voltage in excess of standard charging voltage - 13. Alternator not charging when hot. The alternator will not be damaged by submerged under water. 800 to 11,000 rpm speed range. 8 and use that number on the X-Axis of the below graph. If the battery is not at full charge, the terminal voltage will be lower. (a one wire alternator may require 3,000 rpm to start charging) Check the battery voltage. They also did not factor into the equation that the large drive pulley of an engine spins the small alternator pulley 5 to 7 times faster than engine rpm. On my 2000 Astro, 197,000 miles, the alternator cuts out at high rpm. Caspers Field Fix harness is the quick fix. The battery is a little pickier about its charging voltage. 2006 Chevy Trailblazer 4. The measured voltage should be: * 14. The alternator output should be near to, or exceed the alternator rating (80F ambient). Powermaster uses a state-of-the-art computer alternator dyno to. It would take a hurricane force wind to turn a small wind turbine fast enough to even start charging a battery. If that does not work you either have a bad alternator or a dead cell in your battery…good luck. When at idle the alternator is charging very little & will start charging well at 750 rpm & up. 660W comes from multiplying my 55 AMP alternator X 12 volts. 5k rpm if that makes any difference? I will have a look at the belt, is there any way to. ALL of these systems can struggle with low speeds or power losses from dirty, loose connections Trying to use many accessories results in having to turn off things as soon as it is not feasible to maintain 3500 or more RPM The Omega alternator effectively doubles the charging output, and can do it at significantly lower speeds while keeping up. Now I am confused. If there is a resistor, check the contact of the light socket leads to the flexible printed circuit. 43" and the crank has an OD of about 4. An alternator that is putting out a reduced charge will eventually cause the engine to stall and not properly charge the battery, which can cause starting problems. Economic Benefits Balmar alternators pay for themselves. So I guess that the alternator isn't charging at low rpm. Sep 28, 2013 · As you may already know, there is not a more expensive method of battery charging than using a 120/240 volt 60hz (230 volt 50hz) AC fossil fueled generator. Have the NEW alternator bench tested, too. O ne test is not enough if you are diagnosing a charging system problem. A high-output alternator will cost more, but it should save you money in the long run by extending alternator and battery life. 6v at ~900 rpm. Because a car's crankshaft generally operates at around 1,000-4,000 rpm, a car's alternator is designed to put out good charging voltage and amperage around 3,000-12,000 RPM. My car is a 1999 Miata 1. — After alternator energizes, voltage will increase several tenths. The mechanic tested the new alternator while it was acting up and the tester showed it was not charging correctly. People suggested speeding it up by changing the front pulley (65mm) to a smaller one. Test Your Charging and Electrical System. If you are still experiencing charging system issues, then the battery is suspect. The best way to tell,is have the charging system checked at the auto parts store,they will do this for free,but it will be the alternator,if this was helpful,please rate thank you. Jun 01, 2002 · Our sample vehicle has a very high-rpm performance engine, a 7 1/2-inch crank pulley, and a 2 3/8-inch alternator pulley. This can be. The problem may be due to poor grounds between the negative battery post and the alternator. My old alternator seemed to have had a bad slip ring on the rotor that would "float" the brush at high rpms. 4 at idle and 12. With the engine running, turn on the blower motor and the high beams (or other electrical accessories to place a load on the charging system). 12-Volt Alternator Installation & Operation Manual Introduction Thank you for choosing a Balmarr high-output alternator. A heavy duty marine high output alternator produces more power at lower rpm, instead of high output at high rpm- freeway speeds for an automobile. The rotor is the rotational component of the alternator that consists of a coil of wire. when it gets to higher rpm the alt. Is this too high? Alternator over charging? Regulator not working correctly? How can I test it to narrow down the problem(if there is one?) Engine is a SBC with an original delco alternator and external regulator. An alternator bench test is the most definitive way to determine the condition of your alternator. The cut in speed (when alternator starts to charge) should be around 700 engine RPM. This is on a 51 amp Prestolite alternator that is typically used on marine engines. Because those engines ran at high rpms most of the time, the output of a 1-wire alternator is minimal and is designed to start charging at 1200 rpms or greater engine rpms, and will often "drop out" or quit charging completly when the engine rpms drop below 1200 rpms. Keep the engine running and check the voltmeter again. Replacing the alternator at this point usually solves around 90% of the No Charge conditions on any 3. All bikes show some increase in headlight intensity with higher RPMs but if it goes from dim to bright, it is probably the charging system. Then the light came back on, and this time the alternator was not charging at all. Idle is about 650rpm. If it's cold and you just started the truck, it will read high. My alternator (and tachometer) does not kick in until I apply high revs (3500 rpm). We are the premiere place for 1st gen and 2nd gen Dodges as well as a great source for newer models as well. However, at high RPM it would then be exceeding the speed at which it's designed to efficiently operate. A higher reading indicates damaged alternator diodes. Just blip the throttle up past 2k rpm when you first start the car if you are going to be idling long. Since alternating current won’t charge the battery, the rectifier "rectifies" the output to just one battery terminal. The thermal capability of the packaging is critical to the full use of the output drive. Re: Battery Light - Charging Problem? I started having issues with my battery light coming on at around a constant 3000 rpm, both while driving and if I purposely idel it that high. Read your initial post again - here's what's happening. Next load the alternator by turning on dc loads such as lights, radio, etc. If not, the circuit is faulty and the alternator is not charging the battery. In fact, if the alternator is not working perfectly, your Dodge will soon begin to experience serious problems. Pull alternator and take down to shop to be tested. can really pump a charge. If this happens, charge the battery out of the car to confirm it is still good. It should be about 14-15 volts. When the motor starts the alternator begins charging and 12v - no longer is present. The GEN light is on. Even simple things can be overlooked. Not more, not less. Main vehicle charge wire too small or not upgraded - Almost all OEM wiring is going to be insufficient to properly handle the addition of a heavily loaded high output alternator. 2 volts, then start your car and rev the engine to 2,000 RPM. If the driver is a teenager, the alternator can easily hit 30,000 RPM. I have a manual and did some checking. 67V and this does not even consider any voltage drop in the system wiring between the back of the alternator and the battery bank. But in addition, test for an open from battery to alternator output Hook up as above, and with the jumper connections made, slowly bring up RPM and see if battery voltage rises If not, move your meter to the alternator "big stud" (output stud) and see if that voltage rises and if so, to a high level. Alternator Noise. Aug 11, 2011 · More important than the high output current for an alternator is the output at idle or slightly above, because that is where we need the current. com Serving the Philadelphia/Delaware County PA area. VR2), output/charging lead temperature, and battery temperature should be employed. High output and the vehicle's. Note: This CMI-80-ER can deliver over 100A under SAE testing criteria but we only rate this as an 80A unit. This 200 Amp Mustang Alternator is 100% Brand New, not re-manufactured like other companies sell and is tested at the time of assembly. Verify that the charging voltage is about a volt higher (in the 13. If you have a problem with your high output alternator we will repair it at no charge to you for one year! Monster Audio Performance - This alternator was designed specifically for high amperage audio performance in mind. Oct 19, 2016 · Re: Alternator not charging battery at high rpms « Reply #5 on: 19 October 2016, 04:58 PM » To expand on Harv's comments; instead of buying another alternator not to mention the remove and replace of the alternator, consider replacing the voltage regulator set which comes with brushes if I recall correctly. I am not sure if this is a fault with the alternator, or the ECU. I choose a one wire alternator, as the pulley sizes are such that the engine has to operate, only at 725 RPM to see charging. When you "hop up" a stock alternator, you have to sacrifice charge quality in the low end, just like a bigger cam sacrifices low end power in favor of upper end performance. The cause is not always due to an internal alternator fault, such as a faulty winding, rotor, rectifier or control unit. So I looked at the alt. 6 volts until i rev to 3500 rpm, then the volts at the battery goes up to 13. - i got a "rebuilt" alternator from a parts store and the voltage regulator was only charging 12. This causes the alternator or generator to charge at full output when rotated. first if the alternator stopped charging would that also effect the ac pulse. HIGH-SPEED ALTERNATOR Beginning with the 1983 Camry, a compact, high-speed alternator with a built-in IC regulator is used on Toyota vehicles. If the excitation current is not present at all, the alternator will never charge. Doing the drop voltage test as I indicated above will find out if resistance in the cables is present. 2 shows fine on idle but it drops at higher rpms when turning on heat or others ,goes to eleven or so. It is load related. Velocity Alternator - Providing the Aftermarket and OEM with Reliable High Output Alternators that are 100% Brand New, Direct Fit and Made in the USA. Alternators can take high speeds up to 20,000 RPMs for short periods, so overdriving the unit is not a problem. Increase and hold engine speed to 2000 rpm. Alternator not charging. If you spin it too fast you will loose all output from it, and be strictly relying on battery voltage at high RPM. If the alternator is not receiving power from the ignition switch then it isn't going to generate power. The alternator has two set points for the charging current to the battery as follows: At approx 900 rpm the alternator should give you an output current on the ammeter of up to 2 Amps, at approx 1900 rpm the meter should read more than 1. At lower RPMs, the coils are not capable of making enough current to damage them. An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed. (When you hit the gas is when the alternator is trying to put out a full 100 amps. 3 out of 5 by 3. The alternator is externally excited. '68 145, charging system long ago converted to later sytle bosch aternator with external regulator. The alternator output should be near to, or exceed the alternator rating (80F ambient). open circuit in sense wiring or high resistance. This time they gave me a brand new alternator. Someone told me that I should change the regulator on this alternator to make sure that it does charge at idle. One of the first symptoms of a bad or failing alternator is the need to jump start the vehicle on a regular basis. 5,000 RPM alternator shaft speed is normally required to reach maximum output. The Delco 10SI alternator doesn't need a high rpm kit. Checkout the charging system as indicated and service if required. I took this days ago so I may not remember everything in detail. If the battery is charged though it seems to be okay. It could be the regulator which could be internal to the alt or external. It IS charging, just not as much as you'd like to see and that's probably due to the idle rpm, which in your case I think 800 is normal. 660W comes from multiplying my 55 AMP alternator X 12 volts. Is this a classic knackered alternator. Typically alternator speed is about 2-2. We found that they had connected the voltage regulator to the horn relay for some reason. If so, this is well worth investigating in the event your car battery is not charging. When the engine stops rotating, it turns itself off. 5 VAC with the engine running. Powermaster uses a state-of-the-art computer alternator dyno to. Good, tested, new, alternator. Please read my original post again. If the excitation current is not present at all, the alternator will never charge. A bit of history: this past summer, I replaced the regulator after the "Alternator Workshop" light came on, and measuring voltage at the battery showed that it was charging at a little over 15V. Prematurely aged or faulty vehicle battery. I need to charge a 35Ah 12V battery. Once you hit the "excitation voltage" at the hiher RPM's, it will then charge at idle. If the output of the alternator is dropping to 11 volts at the output wire terminal on the alternator, it is not charging the system properly. Designed for highly (electrically) modified cars - this alternator will quadruple the charging capacity at all RPM Ranges with only minor modifications. The Ford operates at higher rpm anyway so it is not a problem. As the alternator drops back to normal charge, the tach slowly drops to read low when the alternator is barely charging - perhaps 900 rpm where it should be 1500 rpm? (added on edit) Let's think about how an alternator works - the stator turns to excite the fields (or the Field excites the stator). [Editor] To initiate charging upon startup, the small wire going into the rear of the voltage regulator must be at 12 volts. Works fine if you rev it up. 2700 RPM MAXIMUM!. 4 at idle and 12. Its not a real big issue if you dont want to fix it. I have heavy 4 gauge with inline fuse to alternator from battery also kept the factory wiring hookup as well mine charges at 700 RPM 14. The stator reads some ohms (above zero). I installed 130 amp fuses because they came with the very inexpensive and high quality fuse blocks I sourced. My Profile My Preferences My Mates. This is on a 51 amp Prestolite alternator that is typically used on marine engines. 2L pickup’s OE alternator is intended to spit out 150 amps and we’ve found an option for a 2017 Chevy 2500 pickup alternator that will crank out 220 amps. This unit puts out a whopping 220 amps at just 2,000 Rpm's. It's purpose is for the vehicle to run once it's been started. DB Electrical says they are looking into the issue on their end now. 8L V8 (352c. Sep 20, 2018 · If not, the circuit is faulty and the alternator is not charging the battery. 1994 ls400 alternator not charging - removed the alternator & took it to a local shop that rebuilds starters & alternators - guy says its putting out 14. I couldn't make mine self excite no matter how high the revs. Prematurely aged or faulty vehicle battery. Suggesting that people can fit another alternator to a modern engine bay in the currently used 'tugs' is not realistic for sure as Terry said. [Editor] To initiate charging upon startup, the small wire going into the rear of the voltage regulator must be at 12 volts. When it runs in its normal speed range (about 2000 to 10000 RPM), the voltage regulator that is designed to work with it keeps the output at the proper voltage for charging a 12 volt automotive battery (about 14 or 15 volts). Once the rpm lowers, it will start charging again and the light will go off/gauge return to normal. Change the alternator. The RPM range of a garden tractor is a close match to a car, so you really do not need to change a pulley on the alternator like you would on a low rpm motor for best usage. This alt is not self exciting so you do have to get it to around 1500 rpms to get it to work. 2V at the alternator to battery lead when running. An alternator is able to produce power via the electromagnetic relationship of its rotor and stator. Apr 01, 2001 · Taking Charge of Alternator Problems. I indicated that by the time before I removed the alternator, the Battery not Charging message was on solid. BALMAR produces a series of high output marine alternators. Caspers Field Fix harness is the quick fix. High output alternator, which size? This is a discussion on High output alternator, which size? within the Stereo and Electronics forums, part of the General Help category; I have the stock Monsoon amp and speakers and soon to do Infinity's in front using the Monsoon amp. Nov 30, 2017 · Thanks for info. 67V and this does not even consider any voltage drop in the system wiring between the back of the alternator and the battery bank. The problem may be due to poor grounds between the negative battery post and the alternator. Of course, the higher RPM helps the alternator to charge the battery, too. If charging system can operate ALL electrical loads AND Maintain 13. It is most commonly used in. 5,000 RPM alternator shaft speed is normally required to reach maximum output. So I guess that the alternator isn't charging at low rpm. I will try and disconnect the ALTC (B18) wire and test it out. Mar 11, 2011 · At that point in this slowly degenerating process, you can pull your alternator, test it on an external alternator testing machine and see that it's still performing perfectly. Not more, not less. Well Ive been having some charging issues lately on my 2002 gmc 2500hd 6. These curves show amperes vs shaft rpm at 14. On the way home the alternator light stayed on, took it to a shop, on their digital tester it was cycling 3-7-9. breakdown obvious after 19 years …. Probably 3:1 so a 2400 rpm alternator shaft speed would translate to a 800 rpm engine speed, but I certainly am not sure of the Alternator Shaft ratio to Engine Crankshaft Pully ratio. [Editor] To initiate charging upon startup, the small wire going into the rear of the voltage regulator must be at 12 volts. All their performance charts show rpm's at the alternator not the motor. It IS charging, just not as much as you'd like to see and that's probably due to the idle rpm, which in your case I think 800 is normal. I can always up my idle speed but am looking at another option. At about 1250 RPM idle I was getting about 12. At idle speeds of about 650 RPM it can only produce 50 amps or so. Symptom: You start your car, and the alternator won't charge until you blip the throttle to 3 or 4,000 rpm The issue: Doug Tompsett found some information on it, basically it boils down to the 'exciter wire' not doing it's job. Just pointing out that fact. Battery voltage is about 12. A bit of history: this past summer, I replaced the regulator after the "Alternator Workshop" light came on, and measuring voltage at the battery showed that it was charging at a little over 15V. Mostly they are designed to never overcharge, and as such, will drop to mid to high 13's relatively quickly, but all vehicles will vary in the max voltage and for how long it is held. Tested 4 times!!! These new high output alternators can't make power down at idle. Nov 17, 2009 · It will be the alternator that is the problem,the gauge would show charging but the battery light would come on if it was just the battery,most likely the problem. EZ to test with your VOM at the alternator lamp. Re: alternator charging then stops at high rpm Using digital multi meter. High RPMs, temperatures and dusty conditions can ruin them. The alternator does not appear to be charging the battery on our 1970 Mustang. I have no idea why the alternator is not charging below 2,800 RPM but if correct it is either a faulty alternator or an incorrect pulley ratio. The output of high amp alternators can drop off substantially under 2400 rotor RPMs. If you need efficient low rpm charging qualities, it requires a whole new ball game to get there as far as alternator design and internal componentry. I disconnected the alternator cables and started the engine to see if the light will come on with the alternator disconnected, but no , it didn’t come on at all. It supposed to go up to 13. 74Wind, yes, belt is tight. Then the light came back on, and this time the alternator was not charging at all. Before replacing the alternator, additional components should be considered as a cause of failure and checked. My Duratec has a 40amp Brise alternator with 75mm pulley, at 1,000rpm idle it's not charging although the ignition light goes out. 3 while idling. Dec 20, 2016 · That’s what makes a high-output 3G a great upgrade for any Bronco or F-Series owner running either of the alternator’s predecessors. A high voltage condition can very well be the voltage regulator which is built in to the alternator unit, but it could also be caused by resistance in the charging circuit. If at idle you alternator is spinning at 2400 RPM this is good news for you, but most modern vehicles that speed is more commonly between 1600 - 1900 RPM. So, this is the 5th time this alternator is going in:crying: Nope, not the exciter wire.