grassy
Well-Known Member
I understand what each guage does but which ..or both..install in an a-body.
Odd question.
Ian.
Odd question.
Ian.
Which guage or both ?
- Thread starter grassy
- Start date
-
What guages are you asking about?
grassy
Well-Known Member
Should I install an amp meter or a voltmeter.
thanks
ian.
thanks
ian.
slantsixdan
=..=
Voltmeters and ammeters each have benefits and drawbacks. I prefer an ammeter over a voltmeter, because it gives an instantaneous, real-time, right-now reading of what is happening (is power going into the battery or coming out of the battery?). A voltmeter gives a more general idea of the condition of the electrical system over time. But gauge and installation quality also factor in; I'd prefer a good quality voltmeter installed in a good and durable fashion over a poor quality ammeter installed in a problematic way.
I would not want both gauges in any one car; too much distraction.
I would not want both gauges in any one car; too much distraction.
Bill Crowell
Well-Known Member
But Dan, you failed to tell grassy the primary advantage of a voltmeter over an ammeter: a voltmeter doesn't require running all the car's battery load current through the ignition switch and instrument panel, resulting in several fewer things that can go wrong. Many a Mopar ammeter has been burned up due to short circuits elsewhere in the car, not to mention that any bad connections or faults within the ignition switch, the ammeter or in the instrument panel will result in a voltage drop to the coil. With a voltmeter, all of the car's load current (except the ignition current, which goes through the ignition switch only) stays in the engine compartment where it belongs.
A voltmeter will give you just as much information regarding the charging state of the alternator and battery as an ammeter will if you know what the voltmeter reads when a good battery is charging, versus what it reads with a bad battery or when the alternator is not charging the battery.
Ammeters are 20th century technology. We're in the 21st century now. That's why all modern cars use a voltmeter instead.
A voltmeter will give you just as much information regarding the charging state of the alternator and battery as an ammeter will if you know what the voltmeter reads when a good battery is charging, versus what it reads with a bad battery or when the alternator is not charging the battery.
Ammeters are 20th century technology. We're in the 21st century now. That's why all modern cars use a voltmeter instead.
cudajim
cudajim
I think you're both right but I still like my ammeter because you can see instantly how much current is being drawn at any one time. For instance, if you are not sure if you headlights are on (in the daytime) you can simply look at the ammeter and it'll give you a clue.
slantsixdan
=..=
...neither does an ammeter. See for example how Chrysler set up the ammeter in '76 A-bodies and most of their other '71-up passenger cars.
My cars were all made in the 20th century. I'll upgrade various systems and components as I see fit, but I'm keeping my (upgraded) ammeters. If I wanted a 21st-century car, I'd go buy a new Subaru or something.
abodyjoe
Well-Known Member
thats one thing i like about the amp gauge. i caught a broken fld wire on the alt twice while out driving because of the amp gauge. saw it right away.
I've decided to use both an ammeter and voltmeter in my custom dash. Might be overkill on the ammeter & voltmeter but with both I will know what's going on with my electrical system.
Wylde1
"No Value Added" Member
I know Chrysler has used 100 amp alternators in some M-bodies. So how'd they do it and keep the ammeter?
I'll have to replace/upgrade the hacked up wiring harness in my Demon eventually. With twin electric fuel pumps, electric cooling fan and eventual electric water pump and killer sound system, the lil' 30 amp alternator won't cut it. I've thought about the small high amp alternators posted in the past. Should I just replace the ammeter with a voltmeter?
Wylde1.
MopaR&D
Nerd Member
Running both doesn't really make sense to me because in most cases people switch to voltmeters in order to get rid of the dangerous factory ammeter setup. The only real advantage is safety. So if you're thinking of running both for whatever reasons you might as well just run an ammeter because it will tell you everything a voltmeter does (and more). You're just wasting time an money installing a second gauge that tells you pretty much the same thing as the first.
Im not 100% percent sure what caused this, thinking Voltage regulator hatched causing an over charge. but this is what happened to me last fall. Have a new Denso Alternator/Volt meter either are wired in yet but hope this never happens again Also a $500 dollar touch to a new dash harness from Yearone D
slantsixdan
=..=
External-shunt ammeter rather than internal-shunt. Virtually all the current stays on the engine side of the firewall. All ammeters are really milliammeters; only a tiny amount of current actually swings the needle. The rest goes through a shunt. If the shunt is internal to the ammeter, all the system current goes through the gauge. If the shunt is external, only the tiny current needed to operate the gauge goes through the gauge.
The stock internal-shunt ammeter is not "dangerous", and it's perfectly adequate for stock charging systems...especially if the connections are cleaned and tightened once every couple of decades whether they need it or not. Throw a high-output alternator into an otherwise-stock system, and yeah, things are going to burn up. That's not because the stock system is "dangerous', it's because tossing a high-output alternator into a stock system is halfaѕѕed. The '73-'76 A-bodies with heated backglass got 65-amp alternators and 8-gauge main charging cables separate from the rest of the engine wiring harness...right from the factory. And yet we see joker after joker toss a big alternator in his car without changing anything else, and then blaming the predictable result on the stock system being "dangerous". Horseapples!
Go take a look at R/T Engineering. They can rework stock ammeters to handle up to 70 amps efficiently, and they can convert stock ammeters into voltmeters (complete with a new gauge face that looks like factory equipment). Their website's got a bunch of really good info on it, but you have to mouse around awhile to find it; the organisation isn't completely obvious. For example, I know there's a pic of one of their voltmeter conversions somewhere on the site, but I can't find it at the moment! Be sure to see this page. They actually have intelligent, Mopar-owning and -driving people who actually answer the phone, so if you get fed up trying to find what you want on the site, call them.
I used their electronic limiter on my '71 Dart, and now since I need to go in the dash of my '73 to replace a dead temp gauge, I figured I'd beef up the ammeter in prep for swapping on a late-model alternator. Should've called RTE before I bought a good used ammeter off eBay intending to send it into them for upgrade then swap it in, for two reasons:
1. The eBay seller (finally) sent me the wrong ammeter. It's a '76-only A-body ammeter, which is an external-shunt type unit. I could swap it into my '73, but I'd have to create an external shunt on the engine side of the firewall, of the correct capacity to make the ammeter read correctly (depending on the output of my alternator). Certainly doable and not too difficult, but:
2. RTE informed me when I did call them that they have upgraded A-body ammeters for sale on the shelf, either with good used/cleaned-up faces or with newly-restored/reprinted faces. I picked the "good used/cleaned up face" option and the one that arrived is really nice.
Wylde1
"No Value Added" Member
Right on. Thanks for the straight up answer Dan. That's what I wanted to know. Your knowledge is greatly appreciated. I'll be calling R/T Engineering soon.
Wylde1.
Wylde1.
Bill Crowell
Well-Known Member
Wylde1, before you praise Dan's knowledge of Mopar electrical systems so very highly, check the schematic on your car and see if you can find the "external (meter) shunt" that he's referring to. You won't, because Chrysler didn't use any "external shunt". That's why Mopar ammeters burn up when the connections are poor: because they have to carry so much current.
Let me cite chapter and verse on this, since I'm sure Dan will say I'm full of bull (he always does when anybody disagrees with him). In the schematic for my mid-70s model Dodge, the wires going to the ammeter are labeled "S1A-6RE" and "A1-6BK". Anybody with the slightest knowledge of Chrysler schematic nomenclature knows this means that one wire (wire no. S1A) is a 6-gauge red wire, and the other one (wire no. A1) is a 6-gauge black wire. (10 gauge on 35-amp-equipped vehicles: still a pretty big wire).
Question: why did Chrysler use 6-gauge wires going to the ammeter unless they had to carry the full battery load current? If there really was an "external shunt" in the engine compartment that passed almost all the load current, diverting it from the ammeter as Dan claims, then they could have used an 18-gauge wire or smaller from the "external shunt" to the ammeter, like they used for the rest of the low-current circuits.
Now let's follow wire nos. S1A and A1 on the schematic from the ammeter and see where they go. First, they both go through the firewall in their own special, high-current bulkhead connector, not through the regular multi-pin bulkhead connector that the low-current circuits use. If there was really an "external shunt", that bypasses most of the load current from the ammeter as Dan claims, then why was it necessary to use the special high-current bulkhead connector? Hmm??? (On 35-amp equipped cars, both wires do go through the regular bulkhead connector, but again they then go directly to positive battery terminal and the alternator output terminal with no shunt.)
Continuing to follow the schematic, wire A1 goes directly to the alternator output terminal. No shunt in that line!
Wire S1A goes directly to the battery terminal on the starter relay. No shunt in that line either!
Now let's look at a schematic for a 1960 Valiant (before a 100-amp alternator was even a gleam in the engineers' eyes). Wire J1 goes from the ammeter directly to the "battery" terminal of the ignition switch. Wire R6 goes, via the headlight switch, directly to the output terminal of the alternator. And wire A1 goes directly to the battery terminal of the starter solenoid. No shunt in those circuits, either!
Moreover, there's a fusible link in the ammeter circuit. A fusible link would serve no purpose if the ammeter circuit carried only low current, as Dan claims. A fusible link only serves to protect the circuit against extremely high current draw, such as that caused by a short circuit, and Chrysler only used them in high-current circuits.
Furthermore, read through the official factory service manual for these cars. You won't find any mention of any "external shunt".
In other words, between 1960 and the mid-70s, Chrysler used no so-called "external (ammeter) shunt", regardless of whether the car used a standard 35-amp alternator or a 100-amp one.
I rest my case. Whatsay, Dan?
Let me cite chapter and verse on this, since I'm sure Dan will say I'm full of bull (he always does when anybody disagrees with him). In the schematic for my mid-70s model Dodge, the wires going to the ammeter are labeled "S1A-6RE" and "A1-6BK". Anybody with the slightest knowledge of Chrysler schematic nomenclature knows this means that one wire (wire no. S1A) is a 6-gauge red wire, and the other one (wire no. A1) is a 6-gauge black wire. (10 gauge on 35-amp-equipped vehicles: still a pretty big wire).
Question: why did Chrysler use 6-gauge wires going to the ammeter unless they had to carry the full battery load current? If there really was an "external shunt" in the engine compartment that passed almost all the load current, diverting it from the ammeter as Dan claims, then they could have used an 18-gauge wire or smaller from the "external shunt" to the ammeter, like they used for the rest of the low-current circuits.
Now let's follow wire nos. S1A and A1 on the schematic from the ammeter and see where they go. First, they both go through the firewall in their own special, high-current bulkhead connector, not through the regular multi-pin bulkhead connector that the low-current circuits use. If there was really an "external shunt", that bypasses most of the load current from the ammeter as Dan claims, then why was it necessary to use the special high-current bulkhead connector? Hmm??? (On 35-amp equipped cars, both wires do go through the regular bulkhead connector, but again they then go directly to positive battery terminal and the alternator output terminal with no shunt.)
Continuing to follow the schematic, wire A1 goes directly to the alternator output terminal. No shunt in that line!
Wire S1A goes directly to the battery terminal on the starter relay. No shunt in that line either!
Now let's look at a schematic for a 1960 Valiant (before a 100-amp alternator was even a gleam in the engineers' eyes). Wire J1 goes from the ammeter directly to the "battery" terminal of the ignition switch. Wire R6 goes, via the headlight switch, directly to the output terminal of the alternator. And wire A1 goes directly to the battery terminal of the starter solenoid. No shunt in those circuits, either!
Moreover, there's a fusible link in the ammeter circuit. A fusible link would serve no purpose if the ammeter circuit carried only low current, as Dan claims. A fusible link only serves to protect the circuit against extremely high current draw, such as that caused by a short circuit, and Chrysler only used them in high-current circuits.
Furthermore, read through the official factory service manual for these cars. You won't find any mention of any "external shunt".
In other words, between 1960 and the mid-70s, Chrysler used no so-called "external (ammeter) shunt", regardless of whether the car used a standard 35-amp alternator or a 100-amp one.
I rest my case. Whatsay, Dan?
excuse me but Hey Bill, Do you think there might have been external shunt amp meters used in 76 models ? Your mid 70s manual wouldn't be much different from early 60s. The world really is round wheather your book says so or not.
Bill Crowell
Well-Known Member
redfish, checking the schematics in both the 1977 and 1978 Dodge factory service manuals, neither of them shows any "external (ammeter) shunt". I would suggest that you direct your question to slantsixdan. Why don't you ask him to point out where the alleged "external shunt" appears in the schematics?
Yes, there's a shunt, all right, but it's in the ammeter, not in the engine compartment as Dan claims.
The sine qua non of the argument is the very well-known fact that Chrysler ammeters burn up if the connections are poor. The only way this could happen is if the ammeter carries a large amount of current. If there were any external shunt, the ammeter wouldn't carry very much current and therefore wouldn't burn up when the connections degrade.
Moreover, using a so-called "external shunt" in the engine compartment, as Dan claims, would be extremely poor engineering practice and would cause electrical fires if the shunt ever failed. This is because if the shunt opened, all the battery load current would try to flow through the ammeter circuit, which would not be designed to handle so much current and would overheat.
Yes, there's a shunt, all right, but it's in the ammeter, not in the engine compartment as Dan claims.
The sine qua non of the argument is the very well-known fact that Chrysler ammeters burn up if the connections are poor. The only way this could happen is if the ammeter carries a large amount of current. If there were any external shunt, the ammeter wouldn't carry very much current and therefore wouldn't burn up when the connections degrade.
Moreover, using a so-called "external shunt" in the engine compartment, as Dan claims, would be extremely poor engineering practice and would cause electrical fires if the shunt ever failed. This is because if the shunt opened, all the battery load current would try to flow through the ammeter circuit, which would not be designed to handle so much current and would overheat.
longarm
Car sold back to original owners
Don't know if this will help.
For a 70.
For a 70.
Bill Crowell
Well-Known Member
longarm, I don't see any "external (ammeter) shunt" in your 1970 schematics, do you?
Again, the big red wire from the ammeter on your '70 model goes, via the bulkhead connector, directly to the positive battery terminal at the starter relay. The big black wire from the ammeter connects, first, directly to some some lower-current circuits (below the horn relay on the schematic), thence to the bulkhead connector, and from there directly to the alternator output terminal. There's no "external shunt" anywhere in the ammeter circuit. Moreover, note how the ammeter circuit wires are shown as much darker, heavier lines than the other circuits. This is supposed to tell you that the ammeter circuit is a high-current one. If there were a shunt in the engine compartment, the ammeter circuit would be a low-current one that would appear as a thin line like the rest of the low-current circuits.
Again, the big red wire from the ammeter on your '70 model goes, via the bulkhead connector, directly to the positive battery terminal at the starter relay. The big black wire from the ammeter connects, first, directly to some some lower-current circuits (below the horn relay on the schematic), thence to the bulkhead connector, and from there directly to the alternator output terminal. There's no "external shunt" anywhere in the ammeter circuit. Moreover, note how the ammeter circuit wires are shown as much darker, heavier lines than the other circuits. This is supposed to tell you that the ammeter circuit is a high-current one. If there were a shunt in the engine compartment, the ammeter circuit would be a low-current one that would appear as a thin line like the rest of the low-current circuits.
grassy
Well-Known Member
Wow..didn't mean this question to go this far..however, the information here is absolutely top notch.
The only non stock thing going in this car is set of Bosch headlights off my MG..and it that car could handle them, the Duster should have no probs..oh, and a stereo. ... In my '75, I have or did have a blower engine .
I am dealing with a stock system and from what it sounds like, a volt meter is best even though I could but both in because I am parting out the dash cluster. I am doing this because I am trying to make it easier for Sarah to understand what is happening with the car...and if the gauges are directly in front of her, she will actually look at them..
Ian.
The only non stock thing going in this car is set of Bosch headlights off my MG..and it that car could handle them, the Duster should have no probs..oh, and a stereo. ... In my '75, I have or did have a blower engine .
I am dealing with a stock system and from what it sounds like, a volt meter is best even though I could but both in because I am parting out the dash cluster. I am doing this because I am trying to make it easier for Sarah to understand what is happening with the car...and if the gauges are directly in front of her, she will actually look at them..
Ian.
slantsixdan
=..=
If you're looking for a nice little black box under the hood labelled "AMMETER SHUNT" (or a similar box on the wiring diagram) you're going to be looking a long time, unless you're looking at a cop car or taxi originally equipped with a high-amperage alternator. Those got separate external shunts, such as the one called out in group 8-37-5 of the '74 FPC for Satellite/Coronet with certified speedometer (i.e., cop cars):
On non-cop cars, a section of the main charge feed wire is used as the shunt. Good, solid info on both types of ammeters in Mopars here on RamCharger Central; keep in mind trucks switched to external-shunt ammeters later than passenger cars. The whole post containing the highlighted text (at the link) is worth reading. My '89 D100 had an external-shunt ammeter. A broken one, but an external-shunt unit nonetheless!
Bill, I respectfully suggest you spend a little less time being adversarial on the internet without having all the facts, and a little more time examining the ammeters and main charging circuits in '76 versus earlier-year A-bodies. Also spend a few minutes reading the '71 and '76 Chrysler new-engineering-features books which have extensive descriptions of the move to external-shunt ammeters ('71 except A-bodies, '76 in A-bodies). I'm in the middle of an office move, but when everything's all unpacked on the other end I'll be happy to scan in the relevant pages for you, if you haven't found them elsewhere by then.
In the meantime, this is a '76-only A-body ammeter:
And this is a '70-'75 Valiant/Duster + '72-'75 Dart ammeter:
From the front (gauge face) they look identical, but from the back and underneath they look pretty different, eh? The brass-strap frame on the '70-'75 ammeter serves as the shunt. That's where all the current goes through. The later ammeter is a totally different design; the minor current going through the large coil of wire is what moves the needle, and we see an insulating frame rather than a conductive one, because all the system current does not go through the later ammeter.
Additional discussion of internal- vs. external-shunt Mopar ammeters is here.
Bill Crowell
Well-Known Member
Dan, if you set up any more straw men, I'm going to have my horse eat them!
We were discussing early 70s Mopar A-bodies. grassy, the original poster, was inquiring concerning his '75 Duster. Then you inject an argument that applies only to late 70's to 80s non-A-bodies. Read my posts. I never claimed that late 70s-to-80s non-A-body cars had an internal shunt. Everybody thought we were discussing A-bodies, and then you changed the argument in midstream, without telling anybody, to one that applies only to non A-bodies! Hell, Chrysler stopped making A-bodies before they switched to the different ammeter system that you're talking about! Did you notice the name of this forum? It's "A-Bodies Only". And to make matters worse, you threw in a bunch of totally gratuitous, inappropriate and fatuous ad hominem attacks.
So why are you injecting an irrelevant argument concerning non-A-bodies, and then engaging in personal attacks against your fellow FABO member? I'll tell you why. You don't know nearly as much about Chrysler electrical systems as you claim to, and are trying to appear to be "Mr. Know-it-All" in an attempt to make others think you do.
And you recommended that grassy and others switch to an external shunt system. Tell me, Mr. Smarty-Pants, how in hell would grassy do that? How would he be able to wire in the special 10-gauge shunt wire that you are referring to (referring to without telling anyone, of course!)? How would he be able to obtain such a special shunt wire in the first place, even if he could wire it in?
No, I'm afraid you're the one who needs to cool his jets. As I've told you before, when you push your opinions so hard, even to the point of making straw man arguments, personal attacks and assuming facts not in evidence without telling anyone, all it does is betray your own insecurity about your opinions. It is a very unflattering personality characteristic, to say the least, and I'm getting really tired of it.
We were discussing early 70s Mopar A-bodies. grassy, the original poster, was inquiring concerning his '75 Duster. Then you inject an argument that applies only to late 70's to 80s non-A-bodies. Read my posts. I never claimed that late 70s-to-80s non-A-body cars had an internal shunt. Everybody thought we were discussing A-bodies, and then you changed the argument in midstream, without telling anybody, to one that applies only to non A-bodies! Hell, Chrysler stopped making A-bodies before they switched to the different ammeter system that you're talking about! Did you notice the name of this forum? It's "A-Bodies Only". And to make matters worse, you threw in a bunch of totally gratuitous, inappropriate and fatuous ad hominem attacks.
So why are you injecting an irrelevant argument concerning non-A-bodies, and then engaging in personal attacks against your fellow FABO member? I'll tell you why. You don't know nearly as much about Chrysler electrical systems as you claim to, and are trying to appear to be "Mr. Know-it-All" in an attempt to make others think you do.
And you recommended that grassy and others switch to an external shunt system. Tell me, Mr. Smarty-Pants, how in hell would grassy do that? How would he be able to wire in the special 10-gauge shunt wire that you are referring to (referring to without telling anyone, of course!)? How would he be able to obtain such a special shunt wire in the first place, even if he could wire it in?
No, I'm afraid you're the one who needs to cool his jets. As I've told you before, when you push your opinions so hard, even to the point of making straw man arguments, personal attacks and assuming facts not in evidence without telling anyone, all it does is betray your own insecurity about your opinions. It is a very unflattering personality characteristic, to say the least, and I'm getting really tired of it.
slantsixdan
=..=
Again: The A-body got external-shunt ammeters for '76. Take another look at the photos I posted, of pre-'76 and '76-only A-body ammeters.
No, I didn't, actually. I said that's what the factory didbecause it is. I said I considered doing so but elected not to.
I also provided a fair number of links to external sources so anyone who chooses to read them can make up his own mind what Chrysler did and didn't do, and what he himself will and won't do with his own car.
I also have no interest in a pissing contest with you.
Bill Crowell
Well-Known Member
But the fact remains that your posts are entirely wrong! I told grassy that using an ammeter requires running the entire battery load current through the firewall and to the instrument panel and ammeter. You made a big point of ridiculing my statements. Then when I asked you to support your arguments, you pointed to a system change that was effectuated, at the earliest, in the very last year of A-body production, and still requires the full battery load current to be routed through the firewall and instrument panel, while at the same time claiming I don't know what I'm talking about. The facts speak for themselves. The 10-gauge "shunt wire" that you refer to, which was used in non-A body cars, runs all the way from the engine compartment, through the firewall, the ignition switch, into the instrument panel and past the ammeter. So the the so-called "external shunt" that you cite brings the entire battery load current where it doesn't have to go if you use a voltmeter instead. Your original argument was just total crap! You were obviously just trying to blind everybody with bullshit in order to make yourself look smart, and thought nobody would call you on it. Well, I did.
And oh, yeah, that's really great: you don't want to engage in a "pissing contest" with me after you've already pissed all over me!
Why don't you just admit you were wrong and quit throwing a hissy-fit?
-
