I always thought volt meters were dumb, and I used to love my ammeters, until they changed to the shunt. Since then I think they are close to being useless. I've never had one that actually moved. Well if you watch close you can see it move, a little. And then most of them have no numbers on the dial. So the information is: it's either charging or discharging, A LITTLE.
A volt meter can be installed easily with a small wire because it is a static reading. Once you get used to what it does you can have a pretty clear picture of what your system is doing.
So as of now I changed camps. I put my money on the low budget voltmeter.
I know there are a lot of die hard ammeter guys around, and that is great. Diversity is what makes everything interesting,

If anyone is on the fence here, do a search for something like "Charging Problem" or "Alternator" and I have a feeling that most of the guys trying to help will ask questions about the voltage more so than the amperage.
I have tried to help out a few times and it surprised me how many gearheads don't have a voltmeter handy.
I would recommend after the purchase of your basic wrenches, sockets, screwdrivers, channellocks, hammers, and such, the next tool should be a low cost multimeter. Hell, half of your problems can be electrical. Harbor freight sales one for about $4. Not that bad of a meter either. JMHO.
Squido

 

I always thought volt meters were dumb, and I used to love my ammeters, until they changed to the shunt. Since then I think they are close to being useless.

What do you mean "changed to the shunt"? Unless you're reading less than a milliamp or so, there isn't an ammeter made that doesn't use a shunt.

 

Maybe you are not old enough to remember the real ammeters that took the entire load of the vehicle through the firewall to the ammeter and then back to the engine compartment.

If memory serves me, most all pickups and cars were this way in the fifties. Chrysler was one of the last manufacturers to hang with this design up to the early or mid seventies. I know for sure the vans had in line ammeters until 1974 and possibly until 75 or 76.

The heavy wire required to accomplish a series ammeter gets costly, let alone maintenance to the connections and the safety factors involved.

I've personally seen more than one of the dodge vans fry the main junction that passes through the firewall. A heavy load requires heavy connections and the didn't have them. The pass through connections were basically like 1/4" sta-con push on connectors. That's what I remember.

I'm sticking to my guns about the lack of real movement on the shunt type. To me it makes no sense to take a volt meter and read a voltage drop that amounts to almost nothing and then pass it off as amps with little or no real engineering.

I'm not saying it can't be done that way, with good engineering it no doubt can be done, but look at what you are getting. The ones that have a range in numbers are not even close and what are the ones without a range telling you? The left side of the gauge is discharge and the right side is charge. Most indicators don't get to far away from the center and that is with todays increased accessories and the trend to switch from mechanical to electrical parasitic engine loads such as pumps and fans.
Squido

 

I am old enough to remember and have a degree in electrical engineering as well.

A shunt is a resistor used to shunt the majority of the current around the meter movement. Some circuits have the shunt located in the engine compartment, like GM, and some circuits have the shunt located in the meter, as Chrysler does. No matter which way it's done, there is a shunt involved.

Every moving coil meter is an ammeter, even a meter used to measure volts is an ammeter. The current through the meter movement causes the needle to deflect in proportion to the current. The resistance of a common D'Arsonval movement is about 100 ohms, so it only takes 0.1v across it to deflect it full scale.

I don't think you understand the concept of ammeters as they are/were installed in automobiles. They are placed in the circuit to monitor the current to and from the battery into the main power distribution point. If your battery is fully charged, there will be a mere trickle of current into it, and the ammeter will be centered. The ammeter is not used to measure the current to all the auxiliary devices, unless this current comes from the battery. The lack of a calibrated scale on the meter in no way affects the function of the meter, same way with the fuel gauge and temperature gauge.

 

Sorry kids. I have to agree with Inagaddavida (sorry, no name supplied). I have one of them thar' EE degrees myself and he's 100% right. The big whomper wires go in and out of the meter but the vast majority of the current is by-passed by the meter. The meter only uses (measures) milliAmperes and is "coupled" to the line in shunt in a parallel circuit.

Now to defend the rest of you, "shunt" is usually thought of as a shunt to ground so you guys are also sorta correct but a shunt IS a bypass in parallel either "in line" or to ground as a bypass. A radio condensor (capacitor) IS a shunt element to ground.

Interesting geekoid discussion though for the nerdy among us. LOL
Sorry, we really hijacked this one. I'll take an oil pressure guage.... but I voted for a Voltmeter. If it's not above 12 Volts, you're not charging.

Chuck

 

I voted for voltmeter and idiot light, at least for daily driver. You get used to the meter always be in the same place with the high output alternators that you tend not to look at it that often. So the idiot light is a nice attention grabber.

As far as voltmeter vs ammeter, voltmeter tells me the instantaneous voltage of the elctrical system. That's good info. Ammeter, especially on these older cars with low output alts, is frequently going between charge and discharge. It's certainly possible to calibrate it properly so that it shows the exact amount of current flow, but what does that mean? How long will my battery sustain an XX amp drain before the voltage drops to the point it will no longer start the car? With a voltmeter you know exactly what the charge is in your battery at any time.

 

I have an ammeter and an electric cooling fan. I can see the fan run via my ammeter. It comforts me.

 

idiot light is useful, due to throw alt. belt and the light is on telling you problems are happening now.

 

I need idiot lights
I just can't get myself in the habit of watching gauges.

 

What is it about the ammeter that can make it unsafe ? Is it poor wiring, or the gauge itself that causes fires?

 

The most unsafe part is the use of a shunt located in the dash. This requires that the battery charging wire run all the way into the dash and back again. GM uses a shunt located in the engine compartment, in some cases the shunt is the charging wire itself, and only runs the meter current through the dash.

 

OK I have two Electrical Engineers here.
What I was referring to as the old type is explained here
http://www.madelectrical.com/electricaltech/amp-gauges.shtml

The newer type is the external shunt as used by Ford Motor Company and they refer to it in their wiring diagrams as the Shunt Type. So I got fed some bum information, Consider the source. (Ford Motor Company) And I'll stick to my guns that their remote shunt Ammeters as used 1967 - 1972 did not work very well at all. If you are a non-believer go to fordtrucks.com and visit the 1967 - 1972 section and search for ammeters. You will have all you can read about ammeters that the needle barely moves.
I did reference the old chrysler ammeters and the ford truck ammeters in my earlier post. I have no doubt that you EE's know what you are talking about.
As far a safety is concerned, my opinion is this: An unprotected #10 wire has more potential to be unsafe as opposed to an unprotected #16 or #18 wire. The simple matter of the external shunt being in the engine compartment thus keeping the #10 wire out of the passenger compartment makes the system much safer. Don't forget now, I'm talking about some of the old systems that had no fuseable link protection. Even the ones that did have protection were sometimes replaced with a solid full size wire by the vehicle owner because a lot of them didn't know what a fusable link was. So again I feel that they were more of a safety hazard.
You are entitled to you own opinion here and so am I.
Squido

 

Don't expect much from your "charge indicator" as Ford refers to the gauge.
There is a shunt, but don't look under the dash for it, the shunt is accomplished by connecting the two "charge indicator/ammeter" wires to the same black wire between the alternator and the start relay.
The red wire can connect to the battery side of the start relay, and the yellow wire connects to the same black wire from the alternator, but the connection is very near the alternator.

You may get more gauge action by connecting the yellow wire to the heavy black wire AT the alternator.

I have owned three of these trucks with the "charge indicator/ammeter" and in every case the needle just barely deflects regardless of the load on the alternator.
Do yourself a favor and install a nice voltmeter. You will get a whole lot more information from the voltmeter than from the "Charge Indicator/Ammeter"
Squido

In this case, the ammeter will only read the current going to the battery. If the battery is fully charged, the deflection will be minimal, regardless of the load on the alternator. It might even read even less as the alternator load increases due to the reduction in voltage from the alternator under increased load.

 

I used 14 ga wire and put a 5 amp in line fuse to both the horn relay and junction block.
The "shunt" is at the front of the engine compartment so should be pretty safe.
What happened to all the original cars on here. I only see 5 cars listed with an amp.

 

I did notice that all of the negative information posted pertained to Dodges and Fords, Things that make you go ??????????????



Rocky

 

I am guessing that the bulk of the trouble people have had with amp meters is because they ran the wires through the firewall via a hole that they drilled in the firewall and then put those heavy gauge wires through that hole without a protective grommet. Then insulation on the wires wore away and the wires shorted to ground on the sharp edge of the firewall hole, spectacularly.

I have a properly sized grommet in my firewall and my wires are protected from that particular insult.

 

My vote for volt. I travel for a living and i watch my gauges constantly. Its too late when an oillight comes on if you drove the last 20 miles wtih no oil pressure, or battery light shines as you approach 7 or 8 volts in discharge. Nothing feels worse than slowing rolling to the edge of the road in the middle of nowhere with the idiot lights looking back at you. I guess thats why they call them that.

 

My two project vehicles have BOTH the indicator light in the dash, AND a voltmeter.

I have no interest in an amp gauge that carries big current flow into the passenger compartment. My Father-in-law nearly burnt his Buick Skylark convertible because the gauge was defective, and the heavy wires connected to the ammeter carried enough current to get the gauge REALLY, REALLY, HOT.

A voltmeter is therefore much safer than an internal-shunt ammeter. The little wires powering a voltmeter can't carry enough current to get into trouble.

Indicator lights are handy because they catch your attention; I also use both an oil pressure light and an oil pressure gauge; and a temp light along with a temp gauge.

 

I went with Voltmeter and idiot light. An ammeter can tell you that you are discharging rather than charging, but won't tell you how much time you have left. If I see 11 volts, I know I can take a little time to find a safe place to park if I turn the fan and the radio off, but if I see 6 I need to find a safe place to pull over NOW. The idiot light tells me if I threw a fan/alternator belt before I overheat.

K

 

I choose an ammeter. An ammeter is superior to a voltmeter because it is a better diagnostic tool for analyzing problems in the circuit.

 

I am easy to please everything works for me, the wife on the other hand....well lets just say I voted idiot lights.