First I guess I need to say, "Hello." This is my first post, and I am kicking things off with a question. Ok, I have entered an intro post on another thread. I have a 100A self-exciting chrome alternator on my car. It does not excite until roughly 2300 RPMs. Everytime I slow down to idle it "un-excites." As a result, it does not charge during city driving. (unless you get some room to get into it a little) I don't remember having this problem with a one wire set up before. It seems I remember the alternator staying excited after the initial trip to >2000 RPM until I shut down. Any suggestions? Justice <font color="blue"> </font>
heres a tip: make another thread as your "intro" thread. and describe yourself and your car alot more than you did in this post. theres some guys on here who will give you a helluva rough time if this is all the intro you have. otherwise: where in ohio are you from?
I apologize. I just figured they would click on my screen name and visit my profile info. I didn't want to bore you guys with my personal info. The car is a '51 Pontiac 2 door fastback. I built a 355/350 combo and installed it backed up by a 10 bolt GM rear. The rear combo is an Auburn posi unit with Richmond 3.73 gears. I live in northwest Ohio near Toledo. Justice <font color="blue"> </font>
Do you by any chance have after market pulleys? if so I bet you have an underdrive pulley that's slowing the alternator down too much. mine doesn't "unexcit 'til about 600 rpm! BTW: They're right about the intro... I'd get on that before you get your ass chewed!
Pant-pant-pant....whew! I got my intro posted. Hopefully, I did it in time. You make a good point about the pulleys. I was suspecting the same thing, but all of my pulleys are stock. However, I am not sure about the pulley on the alternator. I have a couple of the chrome ones lying around. I will check them against the one on my car when I get home this evening. Thanks, Justice
many of the high output alternators will not kick in and charge until the rpm is sufficiently hi to do so, the reason is: the stators are wound with heavier guage wire, and in doing so have fewer turns. Fewer turns relate to higher cut in rpm requirements. the only way around this is to use an alternator of a larger diameter, so that the requisite number of turns on the stator can be increased, thus lowering cut it rpm. you can overdrive the alternator so that it is turning faster at a lower engine speed to compensate for this problem. on the other hand, once the alternator has cut it, and became energized it should remain charging at engine idle, albeit at a lower level than a stock alterator would do. basically there is no free lunch, alternators are like engines, they are designed with parameters or guidelines for what is required, more amps often times mean more rpm to get it going , lower amps(stock) relate to lower rpm cut in. about the only way to have both is by going to an alternator with a larger diameter stator, which will make the case size larger. bob
ALRIGHT!!! Now that is an answer!!! Thanks for taking the time to write all of that. I took the chrome pulley off of the alternator last night and have been fondling it all day trying to come up with an idea. I hesitate to put a smaller pulley on it for fear of launching the V belt at RPM's above 5,000. The pulley is an OEM size v-belt pulley. I am probably going to have to go to a lower output (vs.100A). It is either that or use a normal 3 wire set-up. I would be glad to hear any other suggestions. Justice
i have the same problem, i also have a chrome 100amp i wire alt. and at idle my volts are around 10, when im at or above 1500 rpm, they go up to 14 volts, but when it goes back below 1500 rpm, the volts go back down to 10. i know how you feel justice, i hate it, i guess i'll go to a 60 amp 1 wire alt. to.
I am no expert, But I seem to remember reading somewhere that if you dont hook up something to the factory guage or something that the alt wouldn't start charging till higher RPM's. Runs in my mind that it was something about how the thing is wired that is telling it to not kick in till later......????? I am only posting this suggestion to generate some discussion here. I can't give you much help, cause I don't even remember where I read about it..... Maybe someone out there knows what I am talking about. Good luck. JT.
I can guarantee you that sonmeone on this board knows an easy fix. We just have to hope they read this post and respond. Come on GURU"S!!!!! Justice
as previously posted some of the one wire alternators have an additional post to connect the idiot light to, which in turn provides excitation current to the regulator to kick on the alternator at idle or there abouts, but.... that still will not fix the problem of low charging voltage at idle on the 100+amp units. You will still have to spin em up over 1500 or so to see the output get up to a decent charging voltage. most of the 100 amp units i have seen are of the same physical size as the more common stock type. as i said before there is a trade off by using one. You get max amps at highway speeds, but the alternator will likely be lagging when idleing. if you want or need more current at idle speeds, then go back to the stocker, or step up to a larger in diameter alternator. I know this isnt traditional, but an option would be to mount a prestolite/leece neville alternator, such as the 270-jb or the new motorola knockoff that prestolite is selling. These can be had in a 140 amp version and will charge 90 amps at engine idle! They are stand alone, and require no external regulator or excitation.Cost new: for the prestolite is around 140 bucks US.They can be purchased from about any HD truck dealer. The downside is that they are about twice the diameter of a stock car alternator. bottom line is you have to consider a few things. for high output at low engine rpm you need either: 1. to overdrive the alternator, so that it is spinning above 2000 rpm at engine idle, or... 2. go to a larger diameter alternator I would first analize my current needs, unless you are running a couple of electric fans on the radiator, air conditioning, EFI, a 10 zillion watt sound system, etc. you may not need a high output alternator. if you have a pretty basic hotrod, then the stocker will work just fine, even with a couple of fans, and a decent sound system. i have worked with alternators for many years, have rewound them for other uses etc. i have one that i just finished that will produce 120volts at 600 rpm at the alternator, or if mounted and driven at 3:1 would produce nearly 360 volt, at engine idle!! it has been tested to 480 volts. Reason i am telling you this is two fold, (1) to demonstrate that i know about alternators, and (2) the alterator i just finished while makeing serious voltage can only deliver 7 amps! one subject i could go on forever, there are other design options that could be incorporated into an alterntor that can get around the problem you have. But there isnt much else you can do with some of these alternators bob
Bob, Thanks, I guess I was just hoping I would not have to replace my pretty littel 100A chromey. I reckon I'll call an auto electric shop tomorrow and see about getting this one rewound for less amps. Justice
Justice: any good shop that does a lot of rebuilding, will have a replacement stator to swap yours out with. i would still do a little calculating as to what your actual needs are, and let the guy know what the situation is, he may have a stator that can get you up around 75-80 amps full output and a decent output at idle. be sure to tell him what you have and what you are trying to do. if the guy looks at you kind of puzzled, just thank him for his time and look for another shop. i know of a place here in tacoma, that does all sorts of alternator/generator and starter rebuilding, they also do custom jobs for the rodders and are aware of your special needs. I would think most cities of any size would have a similar shop with the experience you need to get a good match for your application. one other thought came to mind today and that is one of belt tension, i have a customer with a few 6.5 liter diesels with the 120 amp delco alternators, they charge some at idle but not at all unless the belt is tighter than hell. The application these trucks are in they idle alot, and the alternator was spec'd with a smaller than usual pulley and only one belt. This was a poor design in my opinion as the belt has to be so friggin tight, and the belts don't last long in the winter months with all the start and stop, lights, heater, 4way flashers and such. So it goes to show you even the factory setups can be marginal, and troublesome. bob
so brutus it sounds like your the man to ask. I have a 69 ford w/ a stock replacement alternator. I also have a good sized stereo 600+ watt amp. I am looking at getting a 95 amp 3g ford replavment and pully from PA performance (their kit comes w/ a pulley and regulator and some wire harness). Is there another way i should look at this. My truck mostly does around town miles because it ticks so badly. Thanks Garth
Shiva: i personally have not worked internally with fords alternators, except for their larger offerings they put on there mid size and larger trucks. even on their larger trucks, and i am talking about L8000 series with 8.3 series cummins engines they use the same alternator as on a half ton gas pickup. They get by on the diesels by overdriving them up to around 3:1 or slightly better. This enables them to charge at engine idle speeds. what is your vehicle? do you have room to mount a larger diameter alternator? with your 600 watt sound sytem you are consuming a lot of alternator charge capacity with that system alone, especially if you crank it up. Bear in mind that a stock 60 amp alternator at 12 volts is only capable of producing 720 watts, at least theoretically. That doesnt leave a lot to use else where, and when you talk of just puttin around a stocker will likely not keep up. If you use the small diameter(stock body) alternators you will have to increase the ratio to get it spinning faster to get what you want at lower speeds. with you living so close to tacoma, i would have you call "Hap" at standard auto electric here in tacoma, you can detail your needs and he can set you up with something that will fit your application. I see a lot of posts on many different sites in requard to one wire, high output alternators, and folks having trouble with them. The reality is the alternators are doing what they were designed to do, but were poorly matched to the application. If on the other hand you have the room for a larger diameter alternator, i would look to installing a prestolite or a leece neville unit. Then you have a true 90 amps at idle and 120 to 140 amps(depending on model) at full output, and your problem is solved. one more thing worth mentioning if you decide to go with a larger unit, the leece neville units have been in service for many years in over the road trucks, it is likely one of those will outlast you and your rod, as 250,000 miles is not uncommon for these units. They also have intregal voltage regulators, that are externally adjustable allowing you to set the charge voltage from about 13.2 to 14.8 or so, which is nice. on my 55 project for now i am using the stock 60 amp delco, but when the project evolves and my current needs are increased i will be mounting a prestolite 140 amp or one of the new 160 amp units. bob
I was gonna post an alt. question but figured I'd tack it on here: My 48 Chevy runs a pretty hopped up 350SBC with electronic ignition. It has a 60Amp Delco 7127M Alternator. It's wired through a Ron Francis wiring kit. Looks like 10gauge running accross the engine bay to the terminal/fuse block then to the starter solonoid then the battery. Voltmeter indicates 12V or a little more UNTIL I turn on the halogen lights or the supplemental 16"(13amp I think)electric fan. Then she dips down to 10V or below. Does this sound about right? Do I need a higher output alternator? Would one of those chrome single wire's work for my application? Also- I've tried wiring it single wire with the BATT wire and sensing direct to the starter AND I've wired it with the little GM harness they sell at Speedway and it doesn't seem to make a difference!?? THANKS (hopefully brutus is listening!)
i assume the low voltage reading is at idle, is this right. also have you had the alternator tested, to see what its condition is in? Are you using HEI or ? Does the voltage climb when you are up to 2000 rpm or so? voltmeter? in dash or hand held? bob
Thanks for responding! The voltage reading is on the dash aftermarket voltmeter wired between the key ignition to the horn-relay (I think) and doesn't seem to be effected by different engine RPMs. It'll jump to over 12 for about 5 secs after starting then hover around 12 until I turn on the lights or fan. It's running HEI. The alternator has been tested and I even replaced the internal voltage regulator. ??????
all I know is that I do not want to run any one wire alternator on my cars. My reasoning for this is two fold- One I do not lose any sleep having an extra wire running from alternator to switch and Two I appreciate the lack of having to rev to excite it to charge then wondering if it will require the same rev up to accomplish a charge if rpms drop or engine is restarted. ALSO a valid question is this-are one wire alternators available at all [or most]of our chain auto parts stores or are we bummin if we lose one on a rod run or trip?I try not to use any"exotic" parts of any nature so I don't have to retol mounts or wiring changes for an on the road repair.you know that if it can happen it probably will......also it wont happen always near a quality repair facility with well stocked parts shelfs- it may happen in the middle of nowhere on a Sunday .Just my experience from 30 years on the road driving hot rods.
Justice, I heard you say something about the belt flinging off at high RPM, a fast cure for this is to install a impliment/tractor belt. The belt will cost an extra couple of dollars, but it will be less likely to stretch or twist while under alot of RPM. An old drag racing guy suggested this to me a few years back when I went through the belt flinging problems. You can pick one of these up at a tractor supply store.
noah if you can, get a good volt meter, hand held, and check the voltage at the battery with the engine running. check it at idle, and at around 2000 rpm.. let me know if there is a difference in what the hand held indicates as compared to the dash guage i have seen many dash guages off as much a 2 volts!! and that doesnt help matters at all. Sometimes it is the guage, but most times it is either a nonexistant ground strap from the body to the engine/frame. poor grounding can lead to a lot of confusion, and replacement of unnecessary parts. let me know,, i will try to help you bob
Cool. I'm in texas for 2 weeks but when I get back i'm determined to lick this mutha! I'll let you know. Thanks, NOAH
Ok. Let's see if I can answer some questions. As far as anything under 12 volts when loaded, that means your battery is being drained not charged . If it dropes that much then yes, you need a higher output alternator. My chevy II has a 100 amp alt, and I have a BIG electric fuel pump, electric water pump, dual electric fans, and Silverstar (H4) Halogen headlights, and with EVERYTHING on, it's about 13 volts at idle (about 900 rpm), and around 14.2 at anything over about 1600 rpm. As far as needing anything special for a 1 wire, the case is the same (1 wires are made out of 3 wire cases), so you won't need any special brackets or anything. In fact, the ONLY difference is that the 1 wire has a "self exciting" voltage regulator, and a traditional 3 wire has 1 wire that feeds voltage to the regulator to excite it, and the other wire is for the idiot light. Repalcement parts are exactly the same, minus the regulator.
12 volt batteries are 6 cell units that have 2.2 volts per cell on a fully charged battery, after being nomalized. what this means to you is that the system has to provide at least 12.6 volts to the battery or it will not be able to maintain what it has much less be charged. optimally i would like to see alternators being matched to the application to provide at least 13.0 volts at idle, with every accessory on. 14.2 to 14.5 at cruizing speed, or around 2000 rpm. before i purchased any alternator i would want to see a graph of output, rpm vs amps. i would hold out for one that produced enough power to maintain my battery at an alternator speed of around 1500rpm, The problem i see with most folks and their alternator purchases is.. manufactures are sometimes less than honest.. an alternator that needs to turn 2500 rpm or faster to produce 100 plus amps would be ok if it was able to produce at least 65 amps or so at around 1500 rpm. regrettably i have seen a lot of alternators that simply had the stators changed, and the regulators hot rodded, stuffed in a fancy chrome case, and the end result is yes it will put out the 100 amps as advertised but isnt capable of producing much of any amps at engine idle speeds. These type of alternators, are what gives alot of folks a bad time.. also there is no big trick to making a one wire alternator, the one wire units have the external connections just made internally. i guess bottom line, i wouldnt buy an upgraded alternator until i knew what my needs were, and exactly what the manufacture was offering. Check the output curve graphs. calculate your idle current needs with everything running, add to that at least 20 amps for the battery charging. for instance if you determine that your needs are around 60 amps (electric fans, a/c, extra lighting, sound systems or whatever total) plus the 20 amps to charge will mean you need an alternator that is capable of producing 80 amps at engine idle. most cars use a 2.5 : 1 ratio, give or take a little. so if you idle at 550 rpm take 550 * 2.5 and you get an alternator speed of approx 1375 rpm check the manufactures output curve and see what it will produce at around 1400 rpm in this example,, if it produces anything less than 80 amps it will either be maginal or not keep up with your needs. If it will produce very close or exceed your needs then you have a winner. if you cant get an output curve on an alternator,, pass on it and look somewhere else... buyer beware on this one.. a flashy chrome case would be a lot of grief. i hate seeing people spend hard earned money on stuff that just doesnt do what they expect it to do. What i hate worse are manufactures that knowingly put marginal systems in place just to cut costs... bob
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