LS alternator exciter wire voltage Prove it Please!
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- เผยแพร่เมื่อ 7 ก.ย. 2024
- Which is it? 5v, 8v, 10v ???
100% it’s not 12v I’ve proven this will burn up the internal regulator!
How much does a 470 ohm 1/2 watt resistor reduce a 12v source? 2v, 4v, 5v more?
*There’s lots of claims
My 2000 Yukon supplies 10.2v to terminal B at the alternator, where’s this information? Well it should be easily available!
My 2000 fbody pcm puts out 10.2v to the exciter wire with ignition on. So, youre right on.
I've been looking all day and finally found the information I needed.. this video did the job 👏
Thanks good luck on your project!
The resistor just limits the current flowing through the "L" terminal. It's only 1 resistor, so it would only have a voltage drop if the alternator is providing a resistance. A voltage divider is a circuit with 2 resistors in series with each other, and the voltage measured across any 1 of the 2 resistors will be less than measured across both resistors in series (which would be full battery voltage). If the 2 resistors are the same value, like 470 Ohms and 470 Ohms, then the voltage across either resistor would be 1/2 of the supply voltage.
What ever “Magic” is inside this circuit board works. I know it has at least one 470 ohm resister and has corrected my issues with both over charging and amp draw when not in use. Thanks for watching and the feedback! JD
In all the comments I've read so far, this is the first that is accurate!
A alternator shop here in Calhoun Georgia said they have a special regulator to make it one wire and it fixes the problem
A 194 peanut bulb inline has the same resistance as a 470 ohm resistor. I think it brings the voltage down to roughly 8.2 volts. I've used this for the last year and a half and it works perfectly on my junkyard setup.
Interesting, I’ve heard 8v several times now, I wonder if the lower the input voltage the higher the output? I have mine set at 10.2V but it may charge better if I lower it to 8v? Thanks for the feedback I appreciate it! JD
I’ve gone through multiple alternators on my LS swap toyota as well. I think you are referring to the “L” terminal(not the B terminal), btw. It looks to me like you have a voltage drop issue from your battery located in the back. Did you ever figure out why you were frying alternators?
I would go with the stock vehicle numbers over some internet guru. To figure out how much that 470 ohm resistor reduces just put it on end of wire and see what u get. Pretty simple. I wouldn't waste time searching nothing better than practical application. Maybe u should do a quick vid with volt meter showing what u get thru the 470 resistor it might be the straight answer everyone including yourself was looking for. Great work sir with just the right amount of excitement.
I don’t have a simple 470 ohm resistor I’ll have to order one! Great idea, verify what the voltage drop is then compare the result to my reading from the 2000 Yukon. Great idea!
@@HeadFlowInc glad to help out a gear head
I agree, the lack of accurate technical information about these alternators is frustrating. I’m going through the same thing trying to adapt an LS alternator to the engine in my Suburban.
I know for sure my Yukon uses 10.2V but does this change/fluctuate via ecu control?
I guess I’m going to buy a simple 470 ohm resistor and do some testing.
@@HeadFlowInc another option would be to but a potentiometer so you can vary the resistance in the exciter wire and see what effect different resistances (and therefore different voltages) have on the charging voltage.
Some models use a current transformer that will see a increase in load and kick the alternator field voltage a little higher for the increase in amp draw. And when there’s a lack of draw it will reduce the current. Reducing engine load and emissions. Older vehicles use the light bulb in an alternator circuit as the resistor.
Here’s the deal. Wire the L to a 47 ohm resistor then to keyed 12v. F to 12v switched. S to the positive battery terminal. S terminal senses the voltage drop. Especially needed when the battery is moved to the rear of the vehicle. I’m getting 14.3 volts now at idle with the S terminal hooked up to the battery terminal. Without it the voltage drops to 13.9.
That’s a long way to run a single wire, what gauge wire did you use?
A resistor inline doesn't reduce voltage, it reduces current. if the resistor went from your hot wire to ground, that would reduce the voltage on the hot wire. You did right by just using a voltage regulator.
Resistors don't drop voltage, just amperage, current.
All I know is it works, for the first time since going LS my battery stays charged and I’m not burning up the diodes in the alternator. Idunno 🤷♂️
The equation is V=IR. I is current and R is resistance. In the he sloppy and other videos the 470 ohm resistor kept the output of the alternator at about 14.2 volts. As the current load on your car varies, (fans turn on, etc) the battery voltage will drop. The alternator will sense this and charge harder ( more amps and 15 volts if needed) and bring the battery voltage back up to 14.2 ish. So basically it was decided and proved 470 ohm works good to keep the battery at 14.2 ish volts at all current loads assuming your alternator is up to the task. Similar to what the stock Ecu would do but less complicated.
My alternator tested at 14.0v so I’m not sure how/why it would ever need to produce 15.0v+? But with the alternator functioning properly I still need to know what the voltage is after the 470 ohm resistor.
It doesn’t help me if I can’t verify the voltage drop after the resistor. JD
If your battery is really low, like it won't hardly cranks,once the motor is started, then the alternator will hit it with 15 volts (and like 40 amps) so the battery will recharge quickly . As the battery reaches fully charge (say 13.5 volts) the alternator will meet all the electrical load and keep the battery fully charged and output say 14.2 volts. So the voltage after the resistor varies depending on what the battery is sitting at. If you battery is always fully charged you will probably see 10.2 or so like you have experienced. But if the battery is near dead at say 11.5 volts, you will see less than 10.2 volts after the resistor until the battery is recharged by the alternator.
I know I'm late to this video, and I've seen the response that the buck converter is working so that's good enough... But I figured I would explain why the alternators are burning up and why the resistor is needed. Early applications turned on the alternator by providing 12v to the other side of the charging warning light on the dash. When the regulator sees that the alt is not charging the way it wants it to, the regulator tries to pull the L terminal to ground so that the light bulb will light indicating theres a problem. That bulb needs to limit current and in turn see a voltage drop to keep the regulator from blowing up. Similar situation to having a wire and light bulb and putting it across a battery. With the bulb it just lights up. Without the bulb the wire has to take up the entire voltage of the battery, moves a TON of current and blows stuff up within the circuit. Every time you key on without engine running the regulator is trying to pull the 12v you supply to the L terminal to ground. Using the resistor takes the place of the bulb limiting the current and doesnt burn out under normal conditions. You can't find a direct answer to what voltage you'll get putting a 470 ohm resistor on a 12v supply because you aren't providing enough information to produce an answer. The voltage seen will be directly proportional to the resistance of the load. If your only load is the 1 megohm or so resistance of a multimeter, the voltage dropped will be nearly nothing. Yet if you connect a load of 10 ohms, you'd measure about 0.25v. that's why you aren't finding a straight answer to your question. And the buck converter isn't capable of delivering nearly as much current as the straight wiring is, so when the regulator is pulling the L terminal to ground, the buck converter's output sags rather than the regulator hurting itself trying too hard to pull down.
Makes sense, all I know is the little resistor board fixed all my problems. No more dead battery, no more over charging Or eventually non-charging alternator. Plus everyone notices the little White plastic bandaid box I mounted it in! lol. I truly got lucky I guess, thanks for watching and the feedback! JD
I ran the sloppy mechanics plug n play alt/flex fuel harness. Plugs right into your power tap on the holley and you're good to go.
Nice score! I wish Matt would have included technical information on what voltage etc.
@@HeadFlowInc Yeah, idk what it should be. Was curious about just trying the 5 volt sensor output from power tap and see what that does. I saw a guy just use his dash light output on an older car and it worked.
A single resistor is NOT a voltage limiter, it is a CURRENT limiter
All I know is the circuit board works 100% still going strong. The alternator is not overcharging and it just sat for nine months and the battery still had 12 V. Remember, this is the next side or wire not a main charge wire. It does have at least 1 470 ohm resistor. JD
HeadFlowInc as long as your limiting current, that's all that matter. Voltage on the exciter means nothing. It will work with 5v to full charge voltage, but it can't be allowed to draw unlimited current, as this burns it up. GM alternators have worked this way since the first internally regulated unit. Some early trucks came with a resistor in line to the exciter on a 10si alternator, from the factory.
You nede to know the resistance in the regulator aswell to know how much amps is going thru the curcuit. Lets say its 65 ohms over the regulator then you have: 65+470 ohms = 535ohm. 12V / 535ohm gives you 0.022 amps. 0.022x470=10.54V
That’s awesome I appreciate the clear description! I need to verify the GM alternator regulator resistance; based on your example it has to be very close to 65 ohms. Thanks again I truly appreciate it! JD
@@HeadFlowInc No problem, but how ever I think this 10,54V her is the drop over the 470ohm resistor so if you measure after the resistor you probably will only find 1,44V. My guess is that the resistance over the B terminal will be much higher than 65ohms. But then again high school was back in 1990 so I could be remembering wrong. Post your B terminal measures and I can another go with the math. Love your LS porting videos. Any thoughts of visards diggin in the head under the valve seat creating a ventura shape?
Im not sure why your alternator charges 16V. The B pin on your loom is connected to L on the alternator and it requires a charge light. When you turn ign on 12V goes thru light and to L on alternator and grounds there when alternator is not charging. It also acts as charge start. When alternator charges it sends 12V out of L and you no longer have ground and light goes dark. Pin D on loom is S on alternator. S is for sence and can be connected to B+/fat wire on altornator or to + terminal on battery if you have a voltage drop in loom. Alternator will then use this to know how much effort it has to put in. If you dont have a charge light on the B wire(12V 1,2W bulb is 120ohms) and D/S is not connected, thats probably why you need to put in a resistor not to cook battery/alternator. Glenn
Pin C on loom is F on alternator. F is Field and goes directly to rotor and are not regulated by regulator. F is used when ECU controls charge. If you use and old loom with both B and C pin, try to disconnect C pin. You can also use C/F if you have an external regulator.
I’m gonna have to do this my self in the spring. I’m putting an LQ4/4L80e with Fitech 70051 in a 67 C10. Here is how I plan to solve this problem. I’m gonna use two multimeters, one sett for V and the other for amps. Then hook the amp meter between B terminal and L and Volt meter on battery. When I read 14.2V on battery I’ll read amp meter and then move positiv probe from battery to B terminal and read this value to. Let’s say B reads out to 13,5V when battery is at 14,2V and amps is 0,5. Target Volt is 10,2. 13,5-10,2=3,3V/0,5amps=6,6ohms
This was something I was racking my brain over with my swap that's not done yet
I bought some of the resistors but couldnt find any consistent information on the alternator wiring, this is great information, thank you for this video
Also you might want to add a small heatsink to the 10 prong chip on the board, it converts the extra voltage into heat and being under the hood is going to cook it
I've used the converters before to power an arduino in my car that I control leds with
You could waterproof the board by potting it with epoxy, build a small dam around the board with clay and pour in potting epoxy, but if you do that then absolutely make sure to add a heatsink
This is where 3d printers can be helpful too, I printed a small enclosure for mine
It's faster to just measure the voltage of course. Many hobbyists keep rotary pots to set to a given resistance for testing.
I guess if you are looking for that voltage the best way to find it would be to put your multimeter leads one on the B terminal with it hooked up and the source you could probably get away with just you battery positive and that should be the voltage drop
I assume the voltage depends on how much power your battery needs I assume that changing the voltage will change the current since there is a voltage regulator
It's not quite as simple as working out a light circuit using V = A x R etc as you are supplying a voltage reference to an electronic circuit, this does two things it gives the trigger to enable rotor current and also a reference biased voltage to recognise charge voltage with ability to adjust for voltage drop, say you wanted to put your battery in the trunk then physics dictates you will need a slightly higher charging voltage so your reference voltage should be sourced from battery not from dash for reference circuit as in all electrical systems as load increases voltage wil drop, this exciter circuit will see this also and provide an input voltage change to regulator as well as it sees output terminal voltage, if you decrease exciter voltage slightly by increasing resistance you will see a corresponding increase in output voltage as regulator compensates, rather than have a regulator with a preset output voltage it is variable to load and voltage drop indicated by sensor voltage feedback thru exciter circuit, my suggestion is to use a variable rotary type resistor to determine what you require then either use a fixed resistor ( not ceramic type as they are thermally variable) to finalise circuit, keep it simple for reliability, long ago with external regulator alternators you would select the regulator with the output voltage you required as load requirements changed so did system voltage, newer alternators have the ability to charge at higher amperage at lower speed ie idle with modern electronics loads this is necessary as older type alternators cannot keep up and batteries can become discharged with extended idling, do not try to use older alternators with modern efi engine swaps it only ends in heartache, use the one that came with motor at least, if you want to increase the output of alternator cheaply then change the stator windings from STAR connection to DELTA connection (separate star connection then A1 to B, B1 to C, C1 to A for those that understand)this will enable it to increase output by about 80% but with old style regulators this is still only proportionate to load, ie a 50amp will be capable of about 90amp but only if the load is there so as battery becomes charged the output amperage decreases quickly unless you add load like lights etcetera, an old style alternator modified this way still will not charge at same rate at idle like a modern one will the regulator is just not designed that way, hope this helps
Thank you for the detailed description. So far I’m happy with my adjustable “thingy” I installed; it’s been working great by keeping the battery charged. I’ve experimented with setting the voltage on the reducer at 5v, 8v and 10v with all seemingly working I settled with leaving at 5v to be safe. Hopefully it will continue to work… 🙏🏻
Pretty sure you must install a resistor in the ground circuit also to get this to work right. It's what I found. Run 12v through the circuit and see what its giving you. If it's not right, try adding the resistor on the ground also and see then.
The adjustable resistor is working perfectly now, fully adjustable and consistent.
I need to verify what voltage to set it at. I guess I’ll have to buy a simple 470 ohm resistor and find out myself what the reduced voltage is using it.
it drops the field to a amp field of 7.5,. The resistor drops the Amperes... the problem is the amps from your 12v system can run cold cranking amps to 770amps.. much to high. Computer controlled signal is limited to save gas. Modern nightmare. I think this is what I'm going through right now. Did the 10v work for you?
I’ve set mine at 5v and it still works fine. I’d bet a 7.5v would work but I went with the factory reference voltage.
They sell a pigtail at Jegs etc that reduces the voltage for $20.00 ish. JD
May I ask why did you not put a 470 resistor in between a 12 volt line and measure the voltage at the other end with out the adjustable do hickey you bought?
I bought this adjustable reducer years ago for a different reason, found it in my tool box; decided to try it. I didn’t know it was so difficult to find out what voltage to set for the alternator field /exciter wire. Apparently 99.44% of the people just follow what they read on the Internet with no understanding of how/why. If I have to I’ll order a 470 ohm 1/2 watt reducer and do what you suggested by simply testing before and after voltage. Thanks for watching and the feedback I appreciate it! JD
@@HeadFlowInc please do another video showing the actual voltage you get with a 470ohm resistor! Or just do it and just add a comment!
Well the voltage from a 470k resistor would be the same so 12v or 14 depending on the voltage supplied it depend on the load so just 470k and 12v is not enough info
I’ll order a simple inline 470 ohm resistor and test the after voltage. This seems so simple I can’t believe nobody has done it.
@@HeadFlowInc I mean if the 470k works I'd just do that it might just be the resistance not even a different voltage but like I was saying 1 resistor doesn't really change voltage it just limits current and if it limits to much voltage will start falling
Ya i am seeing this video again 3 years later but a resistor doesn't realy change voltage it limits current and if the current is high the voltage will drop but going with a set voltage isn't really the play i am sure you could use an arduino to check the voltage and very the voltage to the alternator for the load but a set voltage probably isn't the answer
All I know is this works and ever one who uses the 470 ohm resistor says it works. What ever it does I’m glad I found out. 👍
@HeadFlowInc are you saying the 470 ohms or the set voltage and if voltage what do you recommend
i understand, way to often were looking for unicorns and people just dont get the fact were not accepting any kind of a substitute, there is a reason for our madness and the proof is in the pudding we make, the reason the pudding turns out so good is because we find that unicorn.
Factory ecu controls the alt. It doesn’t send 12 volts to it. I used a resistor inline and it’s been fine for years.
Did you use the highly recommended 470 ohm resistor? If so could you unplug the alternator and test the voltage you’re seeing after the resistor? I’m very interested in seeing the results! X1000
@@HeadFlowInc 470 ohm in line, I’ll take a voltage reading when I get home for you
I have three swaps done this way
It's cause not enough people that know what the hell they are doing for real have encountered this to come through and put the info out. I'm stuck for months now with low voltage on an exciter wire in a 1993 Seville. I don't know if it's corrosion or someone put too strong a resistor in line. Bulb had been removed before friend bought the car when I took dash apart. So I have voltage now. 9.2 and alternator doesn't turn on. I think this car needs 12 at the exciter
It’s very possible the older 1993 alternator might need 12v, can you run a temporary wire from a 12v source to test/check? If you provide 12v and the alternator starts working it may be the answer.
Are you positive the alternator is in good working order? JD
When you check on a known good system, don't check it unplugged. You need to back probe it. check it for duty cycle.
Good information Thank you! JD
That 470 Ohm resistor you point at on the dc-to-dc converter is an inductor
I’m totally confused on Amperage! I’ve lowered the input Voltage to the alternator to 5v and it made zero difference to the output voltage of the alternator. The key I’ve found is the Amps needs to be below 1a. 🤷♂️
I've been looking for almost about 6 months
It’s like some kind of weird voodoo. Nobody ever explains. They just tell you to buy the resistor wire from Summit Racing or someone else.
Well emf emr physics says diodes make posative and negative. I would have said 1.7v but that 0degree so take it to say something like 40c.. thats 2.4 so 80 would be 1.2 aha :p but then if got .1 drop 1.1 but you see u have batteries makeing the phases.. i gues from what i like to think of as "reluctant" i think but its excited tho everything is dropping and no one knows physics but they no how to use a multimeter and clamp meter.. but they dont understand the true physics that every single thing and device/ hand held testers actually do use! Its all physics but i keep getting close to everything in space and time because it rlly is space and time its waves and we can see that. Which if u know pie physics wise and proper e=mc^2 then u for sure will understand its emf but thats not just it look into c-rate too but for sure emf emr bro
I might be talking to big of "c" but thats wat i mean aha my understandings are still iffy but i get numbers and thats just numbers tho^ but if i knew ur system i could prob tell u :) lol because i look and look and look into every single thing!!! Its not even funny
I love, that for anything to drop there has to be a "shift of 2 or more things which makes 1 or breaks 1, witch means for anything to be made theres to be more than 1 or less then so but to the atmospheric pressure at whitch is always changing then just looked at through a graph from scientests, but everything else be tooken and evolved into what it is now from all these "forces" and that is truly phenominal! 40 hertz resonating at the 11th power makes for levitation and force tho above or below that is still all other maximums in any form of charachteristic. Like theres too much to say about physics but it truly is a matrix
You’re spinning too fast RPM. If you remember the old gm 10&12si alternators you had a “D” slot in the back to ground one of the field brush tabs. It full fields it bypassing the voltage regulator. Same concept here. The rotor has one coil of wire inside and the ends are exposed on the back and the slip rings are attached. From the factory they are spot welded. When rebuilt the new rings are soldered on. There isn’t any mechanical support for the connection. The solder is heavy. When spinning at hi rpm centrifugal force is pulling them out. If the wrong end of the rotor coil touches any metal part of that rotor is will full field. Eventually it will stop charging completely. Also the plug is labeled PLFS. The L is the only one you need key power to. It gets its power through the battery light from the instrument cluster. Simple fix is run a 194 bulb in the circuit if you’re just running key hot.
Very interesting information! I found the 194 bulb is rated as,12v 3.8 watts, this must be a resistance similar to the 470 ohm 1/2 watt resistor everyone is recommending.
I know lowering the voltage to 10v still burned out the diodes resulting in a final warranty swap and my Lifetime Warranty being Voided by Advance Auto.
since swapping the alternator for the 3rd or 4th time, idle time only no driving, tested 7.4v and 5v signal to the exciter/field wire both resulting in an output of 14.7v charging. I haven’t tried lowering it any further but the adjustable dc-dc reducer can go as low as 1.5v.
I’m definitely going to triple check which terminal the reference is pinned to now, hopefully it’s the L as you described! Thanks for watching and the feedback I appreciate it! JD
@@HeadFlowInc what year and model did the motor and ecm come out of? I can look it up at work tomorrow and give more specifics. FYI: some chevy trucks will turn alternator on/off while running for fuel economy. If the headlights are manually turned on that disables the feature.
Also where is the output cable connected? If that circuit is interrupted (ex. Cable pulled from battery) while charging it will cause a spike and can blow the diodes or v reg. Same with ground cable.
The engine is a combo of parts from 2000 and 2002 and runs on the Holley Terminator X engine management.
The alternators we’ve been using are for the 2000-2002 Chevy Silverado; mine is the higher 130a version. JD
Resistors dont drop voltage unless current runs through it. What is it exactly you're trying to accomplish?
I’m trying to set the voltage to the exciter/field wire at the alternator. 12v doesn’t work, it burns up the internal regulator in a pretty short period of time.
I have the adjustable dc-dc setup I need to know what to set it at. JD
@@HeadFlowInc the 470 figure you see on that buck converter has nothing to do with a resistor. That is a an inductor. Which is a coil. And it is 470 millihenries or microhenries. The unit of measure for inductors.
While I'm not familiar with the LS setup, I do know a lot about operating alternators. Is this wire for the dummy light on the dash. The one that typically goes out after the alternator starts producing power...
No light, it’s purely to trigger the alternator to charge. One wire hook up.
@@HeadFlowInc okay, because in other vehicles, the dummy light is the exciter wire. And the light goes out when the alternator starts producing power. You also have a weird issue of the alternator not charging when the engine first starts. I will watch the video again and comment back.
Hey, JD. I'm looking for an answer for ya. It may take a while.
I’m considering buying a 470 ohm 1/2 watt resistor just to do some testing to verify the reduced voltage. It seems like suck a simple detail. JD
@@HeadFlowInc Hi, JD. I've got some info but it's to much for this avenue of connecting with ya'. Will you email? My email addy is. jandj.racing@yahoo.com.
I'll be looking for ya', Jim
👍👍👍
You can accomplish the same results with a 470 ohm resistor, or buy a pigtail with the resistor already in it. I just happen to have the adjustable board style left over from a previous project. Thanks! JD
It sucks I am building a k3500 truck I had the PCm some one got it
That stinks, good luck 👍
Your problem with finding an answer is they might not sell the right alternator
Maybe, it’s just odd every LS1 website says use the 470 ohm resistor yet they don’t even understand what the new voltage is. lol
5 volts
You’re saying it needs a 5v net voltage to Terminal B or are you saying the 470 ohm resistor drops voltage +- 5v?
Hey i know your probably busy but you wouldn't want to port a ford flathead v8 block would you, make good channel content and payment for your time.
I appreciate your offer/support, I’m not setup to deal with a heavy block and I stopped porting cast iron about 5 years ago. I don’t have the space to deal with the mess of cast iron and the associated health concerns. Thank you again for the offer! JD
@@HeadFlowInc hey man thanks for your reply, love your work, keep it up.
Call mechman.com if you have any questions about alternators they know everything there is to know about alternators and make the best alternator period hope that this helps
Yeah, 12 volt not good.
Between my friend Richard and I we’ve burned up at least 7 alternators, Lesson learned!
Now to see if it’ll hold up to 7000 rpm shifts... ?
@@HeadFlowInc Geesh