ammeter to volt gauge

[SRT_DSTRHOLC]

how can i get rid of this horrible thing and go to a volt gauge?

 

[bob shaner]

madelectric.com

 

[Bill Crowell]

74Burtorange, on a stock car with an ammeter, all of the ignition current flows through the ammeter, so it is a fairly high-current circuit and therefore they have to use fairly big wire. But you are going to eliminate the ammeter from that circuit. So what you basically want to do is to remove the ammeter electrically from the circuit by disconnecting the two wires that presently connect to it and soldering them together, so your ignition current will simply bypass the ammeter. Then solder a smaller wire to that same junction; insulate the junction with electrical tape; and run that wire to the positive terminal of your voltmeter, grounding the other terminal. (The voltmeter is a very low-current device, so you can run a small wire to it.)

Technically, the difference in the connection of an ammeter and a voltmeter in an electrical circuit is that an ammeter (being a low-resistance, high current device) is inserted in a series with the circuit load, while a voltmeter (a high-resistance, low current device) is connected in parallel with (i.e., across) the circuit. If you tried to connect the low-resistance ammeter across the circuit, you'd blow something up because it would try to draw infinite current.

 

[SRT_DSTRHOLC]

ok, cool thank you

 

[Demon 408]

how can i get rid of this horrible thing and go to a volt gauge?

It can be done inexpensively if you don't convert your existing ammeter to voltmeter. Check out my electrical upgrades and how I went from an ammeter to a voltmeter at this link: http://www.forabodiesonly.com/mopar/showthread.php?t=73437

 

[SRT_DSTRHOLC]

thats nice, little too much work for me. Safe and nice but i think ill go with the post above yours and just try to make it as safe as possible

 

[Demon 408]

thats nice, little too much work for me. Safe and nice but i think ill go with the post above yours and just try to make it as safe as possible

As was recommended by Bob Shaner, use MAD Electrical web site, he even shows you a schematic. This is the safe and least expensive way to git er done. http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Good luck and let us know how it turns out.

 

[SRT_DSTRHOLC]

too bad i couldent have someone make me one like yours, im not good with electrical, its something i shortcut and shouldent

 

[slantsixdan]

I don't like the hack-azz "solutions" offered at the (chevy-head) Mad Electric site. I much prefer the clean and technically correct ideas and components from 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). They also sell a really good electronic instrument cluster voltage limiter. 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 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.

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. $75 or $99, respectively.

 

[Demon 408]

I don't like the hack-azz "solutions" offered at the (chevy-head) Mad Electric site. I much prefer the clean and technically correct ideas and components from R/T Engineering.

I wouldn't say that MAD Electrical is hack-azz...the hacking depends on the installer doing the work! Although he does speak poorly of the Mopar alternator and highly of the GM one-wire alternator. However, I can personally speak to the quality of the parts and advice that he gives...like it or not...take it or leave it.

 

[slantsixdan]

I can personally speak to the quality of the parts and advice that he gives.

So can I. His advice crosses one of my areas of training and professional expertise, which is why I can say he's at least partly full of it. Some of his advice is conceptually sound but the recommended fixes are not well thought out nor optimal. That's my personal and professional opinion; others' opinions will vary and that's OK.

 

[MadScientistMat]

I wouldn't say that MAD Electrical is hack-azz...the hacking depends on the installer doing the work!

I've got to agree with Dan here - there's a number of recommendations on their site that are hack jobs in and of themselves. It's far from the worst hack job I've seen (I have owned a British roadster before...) but they still have a lot of things on their site that are not exactly good wiring practice, and a fair amount of questionable information.

Consider the CN-1. Putting a ton of ring terminals on one stud can get corrosion forming between the rings, and it isn't nearly as good an electrical connection as one ring per stud like a normal terminal block would use. I've seen this approach run into trouble if you're working with devices that draw a lot of current or are sensitive to electrical noise; switching to multiple studs with one ring per stud often cured the problem. Or the example they have where they're claiming crimps are always bad in the voltmeter conversion article - well, the example they used showed a cheap crimp connector, intended for a different gauge of wire, apparently crimped with a set of $3 sheet metal crimpers, using an unsealed connector in a spot where it had filled up with water! Of course it's going to fail spectacularly. Then they generalize from this worst case and say that all crimp connectors are bad. Not when done right, they aren't. In fact, virtually all connectors in OEM automotive use today are purely crimped with no solder.

The site isn't complete misinformation, but definitely should not be taken as gospel.

 

[Demon 408]

Some of his advice is conceptually sound but the recommended fixes are not well thought out nor optimal...

...but they still have a lot of things on their site that are not exactly good wiring practice, and a fair amount of questionable information. ...The site isn't complete misinformation, but definitely should not be taken as gospel.

I don't disagree with either of your points, nor do I take the MAD Electrical web site information as gospel. Taking anything you read on the web as gospel is dangerous, especially when people are trying to sell you something.

Let's not forget the purpose of the original poster...he was simply looking for information about changing from an ammeter to a voltmeter. The link(s) that I posted were for his consideration in achieving that goal, not to highlight or endorse a particular business or web site.

Peace out...

 

[Bill Crowell]

An ammeter is always connected in a series with the circuit load. Two reasons: 1. you're trying to measure how much current the circuit draws, and the only way to do so is to connect the ammeter in a series with the load; and 2. connecting it across the circuit will make it try to draw infinite current.

I know of a case where, even though she had been warned not to do so, a government radio technician trainee tried to connect an VOM across a stiff high-voltage circuit and it drew so much current that it instantly exploded in her face and killed her. Of course, this is very unusual. Normally it would just(!) burn the circuit up, burn up the ammeter and start a fire.

 

[slantsixdan]

Ammeters aren't the only thing that can explode in yer face if you use 'em wrong. So can chewing gum.

 

[MadScientistMat]

True, the MAD website will accomplish that, if you just stick to what they did and ignore some of the theory. There are two things I'd do different from their conversion, but neither would completely ruin things - I'd crimp the alternator and battery wires to the same ring terminal instead of stacking them, and I would not try drilling the connector and running a wire through it. That one is more a question of style, but I'd use a separate bulkhead connector or extra holes with grommets.