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Amps guage on one wire alt

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billd View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/06/2017 at 11:09am
Originally posted by vinny vinny wrote:

My first vehicle when I was 13 years old was a 51 Thames P/U with 6 V positive ground. The Lucas amp gauge had a piece of cloth covering the right hand side preventing the needle from showing a charge. I reversed the battery and knew that showing a discharge was really a charge. My brother who got the truck after me fixed it by taking a hammer to the gauge. 


The congressman I have worked with has a 69 British sports car and we got to talking about Lucas systems - geesh, I don't see that name very often. He also knew of the Lucas electrical issues of years past.
If your brother is around, maybe I could hire him to help with some of the real problem systems HAHAHA. 
Hammer - that's funny. 
Hmmm, is his name Red Green and is he Canadian, by any chance?  Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Dec/06/2017 at 11:20am
Originally posted by billd billd wrote:


Originally posted by 304-dude 304-dude wrote:

6pakbee, yes you can use an ammeter, and do just fine. Though I recommend decent cables, i assume his alternator can produce 2x the current than stock.

As for ammeter operation, the needle should be a wee over 0 when charging or in operation. I never seen one at 0, unless ignition is off.

I believe in KISS, if your electrical system is not setup for an ammeter then why complicate matters and possibly create a fire risk.

As for knowing how the charging system is going... the idiot light is basically a low budget light emitting current detector. It's not perfect but, it can tell you when a battery drain is happening by a lack of charge or very weak battery condition after start up.

Billd put it fairly straight forward, yet I understand an ammeter can be added, but we must be cautious in expecting good help to be understood and done as well as the experts here. Even an expert can create a good spark or two, so we just don't want to make a big problem of it.


MOPAR alternators since 1970 couldn't run a light. There was no provision at regulator or alternator for a light. 
People were used to TRACTORs, trucks, and old cars with ammeters and knew this side good, that side bad, but what if it reads charging at all times? Depending on the meter, it should not. Do people know that?
But with a volt meter, they can color the scale - and if it's reading in the red below green that's bad, the red above green, that's bad, green is good......... and as a professional, I can look at a volt meter and tell you a lot............ 
Chrysler had to run a meter, since their simplistic system couldn't run a light, and the ammeter had been what everyone was used to. Also keep in mind even in the 60s and 70s we had people driving who were used to an ammeter....... it was a comfort thing then.
Today it's a "cool thing".... but do people even know what they are looking at? Nope - not in most cases - only that they have these cool gauges so it's a hotter car.


Ah, yes i now understand, though i spoke in GENERAL to the TOPIC, and did not want it to turn into MOPAR when it is AMC and possibly a 10SI one wire install. After all his question was pointed at you, and i just wanted to explain reasons why we just don't dive into such things not knowing the skills of the OP, and their choices when making such a modification.

Like you I never bother with an ammeter, even when i have and had rally pack gauges setup or to be setup on my cars. It's not that i fear them, just more work than what it is worth for a car not factory setup for them.

I always leave you, or other experts to elaborate when I am vague in comparison or furthering on the MOPAR path, which I would study before commenting any more than I have.
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Post Options Post Options   Thanks (2) Thanks(2)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Dec/06/2017 at 12:46pm
Originally posted by billd billd wrote:


...Uh,  was going to try to be PC, polite, etc. - but frankly it's frustrating when decades of experience and attempting to convey helpful information is slammed, so... PC out the door - I know bloody well where, why and how to wire ammeters and for that matter, entire cars (from scratch I might add) I know how they work, where Chrysler put them, etc. Remember, I wired MOPARS from scratch after wiring fires. 

So far this AM I don't feel like trying to explain 45 years of experience, formal training, courses in electricity and electronics at the HS and college level, doing this for a living for years, etc. to justify my comments....
 

Well, I am going to be neither PC nor polite.  An ammeter system is cheaper and simpler than a voltmeter system?  In what universe.  Not this one.  As to slamming an attempt to convey helpful information, I didn't criticize you, you are criticizing me.  Do you think you are the only one that has spent 50+ years under the hoods of cars working on electrical systems?  What gives you the right to act like your opinion is the only one that is right?  What gives you the right to dismiss anyone who disagrees with you?  This in my opinion is just another rant of yours where you feel the whole world is ignoring poor little you and the wisdom that just pours out of your mouth.  I've had it.  I am never going to participate in another post where the great God Billd has pronounced the ultimate truth and then criticizes and demeans any conflicting opinion.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote tomj Quote  Post ReplyReply Direct Link To This Post Posted: Dec/06/2017 at 11:56pm
i'm largely with billd here. ammeters were less difficult when total system current was a mere few 10's of amperes. ammeter, vs. voltmeter, requires running the full car load and battery charge through a wire from gennie/alt, to the instrument panel, then back to battery and loads. that's a FAT wire even for 20 amp alternators, plus the potential for harm from frayed wires carrying heavy current. plus voltage drop through all the wire, extra connectors, ammeter itself etc. 

if the car is made for one, it's easier to run, since it's there.

to add monitoring, a voltmeter is vastly easier, and billd's totally correct, you can tell as much or more about battery state with a VM.

also, if you upgrade to a large alternator -- for which i never see the point, eg. 60, 80, 100 amp alts in cars designed for 35 -- that amperage will MELT 20, 35 amp wire to/from the battery, if and when that battery gets very dead (leave lights on overnight, etc).  more current (capability) is rarely better, even with a big stereo and added A/C. 



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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2017 at 2:57am
Matt's keys to getting along with people in the classic car world (I often have to rims myself of these):

  1. Present your opinion/advice as what has worked best for you, not as the universal truth for everybody and all cars.
  2. Listen politely and think about what somebody is saying when they are presenting you with their opinion/advice. You are not obligated to do/follow what they are saying, but you are obligated to be polite.
  3. If you disagree with somebody, it is best to not say anything. Avoid an argument. Just leave the conversation and continue living your life in a way that disagrees with theirs. 
  4. If you choose to openly disagree with somebody and open an argument, make sure to argue point-to-point using concrete evidence or examples. Remain impersonal. Preferably do not quote them or even mention their name.
  5. NEVER attack that person's age, experience, education, or credibility. Nobody cares about those things. They care about the facts and evidence. Personal attacks are a sign of somebody who knows they are losing an argument and is reaching for whatever they can to stay on top. Don't be that guy.
  6. When somebody disagrees with you on a topic or method, they probably do not mean it as a personal insult or attack even if it sounds like one to you. Ripping off their head because you feel insulted only makes you look like the bigger jerk. 
  7. If somebody attacks you personally or you otherwise feel offended for whatever reason, refrain from counter-attacking. Taking another person's negative attitude upon yourself only makes you into what you hate and slowly turns you into an insecure person like them. Only insecure people feel the need to beat down the people around them. 
  8. Stop caring what other people think of you, your opinions, or your car. What they think doesn't matter. Put a big friggin' rooster comb on the roof of your Chevette if it makes you happy. People will call you nuckin' futs, but remember...you don't care. Don't let other people ruin your happiness. They are not important enough to have that kind of power over you. 

Seriously. Topics on cars and politics are so much more pleasant if you keep those in mind. 

-------------------------------

I present to you my impersonal opinions and evidence:

Ammeters with a +/0/- scale don't splice into the alternator output wire to measure alternator output current. They splice into the main power feed wire off the battery to measure current either going into or out of the battery from the entire vehicle electrical system. The alternator will keep up with all electrical loads in the vehicle up to the alternator's current rating. The only current going through the ammeter is either going into the battery to charge it (+ reading) or current leaving the battery to power electrical loads the alternator doesn't have sufficient output to handle (- reading). Unless the battery is severely discharged, extreme electrical loads are encountered, or the alternator fails, ammeters will rarely have more than 15A flowing through them. 

Ammeters are hold-overs from the days when cars had third-brush generators that did not regulate themselves. Drivers had to adjust the third brush as needed to provide proper battery charging depending on what electrical loads were switched on and the engine RPM. The easy to read ammeter provided early motorists with a simple "charging or discharging and how fast" indicator for the battery so they could set their generator brush as needed. Ammeters cannot show battery condition or voltage regulator operation however. Because of their potential for carrying high current, ammeters should always be wired with heavy gauge wire and solid connections. 

Voltmeters work fine and provide more information on battery condition and voltage regulator setting than an ammeter can. Unfortunately that makes reading them a little more complex. Failing or defective batteries can cause very strange voltmeter readings as can faulty voltmeter installation. The voltmeter should take its reading as directly off the battery as possible because current flowing through the vehicle's wiring causes IR voltage drop and you don't want the voltmeter to be biased by that. 

Whether you have an ammeter or a voltmeter, a warning light is always a good idea if your charging system has provision for one. A warning light will catch your attention faster than a gauge reading outside of normal would. The light exists to catch your attention with "something is wrong", but the gauge exists to tell you "this is what is wrong". 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2017 at 6:53am
hi, currently restifying a 77 Hornet AMX. I believe this is the last year of the stock ammeter in the "rally pak" gauge package. I am planning on leaving it in, since I had the gauge package professionally restored at no small cost. This ammeter uses a "shunt". in the engine compartment. How does this work? Anyone educate me please. billd? thanks, gz
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2017 at 7:34am
Excellent question amcfool1 - the shunt type ammeter uses a very accurate resistor of known value. It must be of very low resistance and have a tolerance that is low (can't use a 5% tolerance, for example, like is used in so many electronics).
Having a low value resistor that won't put too much voltage drop into the circuit that is a known value, the shunt is actually a volt meter that measures voltage drop across that shunt or resistor.
The resistor is the shunt.......... thus the name. 
More amperage through a resistance, the greater the voltage drop........ less amperage flow through the shunt or resistor, the less the voltage drop.
I have a Sears Craftsman meter (tach/dwell/volt/ohm/amps) from the 1970s and it operates that way - you put a large resistor in the system and there is a special wire that clips on and measures the voltage drop. That way they can use 18 gauge wires for the leads.

And I think tom or someone brought this up - if you have a so-called "1 wire alternator" these are typically sold to rodders who have the "more is always better" and "more is cool" mind-set - and are usually higher amperage output units than we need or have. 
So............. let's say that 1-wire is a 120 amp unit - you had better measure the length of wire needed, calculate for 120 amps and start putting larger holes and hefty grommets in the firewall. You must plan for the full output to travel through a non-shunt ammeter - into and out of the cabin.
Some will say no, you don't need that as that much won't go from alternator to battery.
Wanna bet?
I had a decent battery charger trashed by a shorted battery. There's also the chances of jump-starting or cranking until the battery is nearly dead and then doing what too many people do "let the alternator charge it" (which is bad idea)

So a shunt type ammeter is a volt meter measuring the voltage drop across a special low-value resistor of extremely tight tolerance (a known value)
A shunt/resistor is placed between battery and alternator, the gauge connects to either side of that.

A typical normal ammeter you need to figure for the full output of the alternator going through it....... just in case things go south. 

Chrysler alternators are A-circuit design, they have two wires. One from ignition to feed the field the other goes to the regulator. The regulator controls the GROUND side for the field. So the field is always hot. Otherwise it has but one wire - the OUTPUT. So there is no driver for a dash light. Chrysler HAD to use a gauge/meter of some sort because their alternator design didn't have a diode trio or isolation diode that allows a light to be used. 
The Delcotron 10si, etc. is also A-circuit field but since it's all internal, and they DO have a diode trio or field diode array inside they can drive a dash light........
The so-called "1-wire" alternators are Delco units that have a third-party regulator in them that senses alternator rotation and "switches on" when the alternator spins up.......... or in some cheapie cases, you have to rev it up to about 1500 to 2000 engine RPM to get it to start charging. 
Anyone with a "1-wire" alternator would be wise to put a volt meter in............ and see if you have the more expensive better design, or some cobbled system that has to rev up high to start charging. 

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Post Options Post Options   Thanks (1) Thanks(1)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2017 at 7:40am
Originally posted by tomj tomj wrote:

i'm largely with billd here. ammeters were less difficult when total system current was a mere few 10's of amperes. ammeter, vs. voltmeter, requires running the full car load and battery charge through a wire from gennie/alt, to the instrument panel, then back to battery and loads. that's a FAT wire even for 20 amp alternators, plus the potential for harm from frayed wires carrying heavy current. plus voltage drop through all the wire, extra connectors, ammeter itself etc. 

if the car is made for one, it's easier to run, since it's there.

to add monitoring, a voltmeter is vastly easier, and billd's totally correct, you can tell as much or more about battery state with a VM.

also, if you upgrade to a large alternator -- for which i never see the point, eg. 60, 80, 100 amp alts in cars designed for 35 -- that amperage will MELT 20, 35 amp wire to/from the battery, if and when that battery gets very dead (leave lights on overnight, etc).  more current (capability) is rarely better, even with a big stereo and added A/C. 


There's another point - if that alternator stops charging, you WILL be running the whole car from the battery so be VERY careful where an ammeter goes! If that alternator ain't charging, you run the whole car, lights, radio, AC, etc. from the battery..........
Volt meters are simply safer, far far far easier to install, and I can tell you a lot more about the system with one. Note that all newer vehicles I own or have owned have VOLT meters. Yeah, the factory could use shunt type ammeters and save on heavy wire, save MONEY and make them cost about the same, so the argument that it's about money is debunked right there.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2017 at 8:21am
Final comments.

What did amxmachine actually ask?  "Want to install an amps guage not concerned about idiot light working. How do i wire this and what amp fuse would i use?".  And I accurately answered with the typical arrangement for a charging system with an ammeter.  I don't care if it's a '48 Chevy, a '69 Dodge, or a '64 Massey tractor, if it has an ammeter it's connected in series with the main feed from the battery to the vehicle.  That's the typical arrangement.  That's a FACT, not an OPINION.  Question asked, question answered.

And then this whole post went off the rails.  Ammeters are no good as they don't tell you anything.  Perhaps to people who are biased against them.  A Mopar charging system can't support an idiot light.  So what?  I'd bet my life savings when Mopar transitioned from a generator/ammeter arrangement to an alternator/ammeter arrangement, that was a corporate decision to retain the ammeter.  They could have emulated GM and gone to an idiot light but didn't. 

As to which is better, pure opinion.  My newer vehicles have voltmeters and I hate them.  Personal opinion.  But it is my opinion and I'm entitled to it.  To me the mark of a truly stable individual is the ability to agree to disagree.  You like blue cars, I like white cars.  Each has its advantages and disadvantages.  But when you start demeaning me for liking white cars...that's crossing the line.

I'm not going to comment further on this thread and in the future I'll make sure not to participate in another peeeing contest like this one turned out to be.
Roger Gazur
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1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote bigbad69 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/07/2017 at 10:25pm
I think a +/- ammeter is more useful than a voltmeter. An ammeter will tell you something is wrong now. A voltmeter will tell you something went wrong some time ago and now you're battery is discharged. It's kind of like an oil light vs oil gauge. The light tells you you lost pressure, the gauge tells you the pressure is dropping - big difference. However, the shunt style ammeter is definitely safer than the full current type.
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