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Amps guage on one wire alt |
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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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? |
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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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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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5457 |
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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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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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tomj
AMC Addicted Joined: Jan/27/2010 Location: earth Status: Offline Points: 7544 |
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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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1960 Rambler Super two-door wagon, OHV auto
1961 Roadster American, 195.6 OHV, T5 http://www.ramblerLore.com |
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FSJunkie
AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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Matt's keys to getting along with people in the classic car world (I often have to rims myself of these):
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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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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amcfool1
AMC Addicted Joined: Jun/18/2011 Location: roanoke va Status: Offline Points: 1075 |
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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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george z
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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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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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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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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6PakBee
Supporter of TheAMCForum Charter Member Joined: Jul/01/2007 Location: North Dakota Status: Offline Points: 5457 |
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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. |
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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bigbad69
Supporter of TheAMCForum Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6668 |
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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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69 Javelin SST BBO 390 T10
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