The Ford Barn

Paul Bjarnason · 03-31-2023, 06:22 PM

I installed a 12-volt alternator in my '29 Tudor and would like to have a voltmeter gauge in the stock ammeter location. But, the stock ammeter hole in the dash plate is only about 1.5" in diameter while available voltmeters are 2 1/8". I found a digital voltmeter which is smaller than 1.5", which I can probably make fit, but I think an analog voltmeter (one with a needle) would look better. If anyone has done this, please inform me as to what gauge you bought, from where, and how you installed it. I think I could bore the dash plate out to fit the 2 1/8" gauge, but would prefer one that fits the stock dash plate. Thanks.

nkaminar · 03-31-2023, 07:36 PM

I did a quick google search for 1.5 inch diameter voltmeter and found this: https://www.autometer.com/1-1-2-volt...075s-elec.html. I did not go further but it looked like there were more.

I have a voltmeter but it is mounted below the Model A instrument panel. I kept the ammeter. The voltmeter is handy and my goto meter to assess the health of my charging system and battery, but the ammeter is handy as a backup and to assess the health of my ignition system. With the alternator, after the battery recovers from starting the engine, and the voltmeter goes to 14 volts, the ammeter shows no charge or discharge. That way I know that the battery is fully charged and that it is happy. When I sit at an idle I can see that the alternator is not putting out by the voltmeter at around 12 volts and that the battery is supplying the current to run the car by the ammeter showing a discharge.

Paul Bjarnason · 03-31-2023, 08:19 PM

I just ordered the 1.5" voltmeter from the source you found. Thank you for the tip. Bj

Charlie Stephens · 04-01-2023, 01:05 PM

Another problem you haven't got to yet is that the space behind the dash is not enough for most modern instruments. Get a bracket and hang it somewhere. Any chance you could just add a shunt to your ammeter and keep it? And in closing, what is wrong with the ammeter?

Charlie Stephens

Charlie Stephens · 04-01-2023, 01:07 PM

DUPLICATE post

nkaminar · 04-01-2023, 01:35 PM

Sponsored Links (Register now to hide all advertisements)

Charlie,

The ammeter can be just kept as it is when adding a voltmeter. The ammeter is handy to have in addition to the voltmeter. Hanging below in my my car is a voltmeter, a tachometer, a temperature gauge, and an oil pressure gauge. All nice to have. I pay more attention to the temperature gauge than any other gauge. Second is the tachometer. The original style ammeter is in the usual place. The voltmeter let me know that my alternator failed on one road trip.

nkaminar · 04-02-2023, 07:31 AM

Pete, A link would be helpful.

gdmn852 · 04-02-2023, 01:04 PM

Hello, I have both voltmeter and battery condition indicators in my MGB , as previous post mentioned, nice to monitor the electrical system. Mine are vintage Smith’s gauges and are as old as the car 1971 and still do the job.On the battery condition,actually a voltage meter, you can turn ignition on before starting car it will show the charge in battery.

Pete · 04-02-2023, 04:07 PM

Quote:

Originally Posted by nkaminar

Pete, A link would be helpful.

No links. There are electronic flea markets all across the country.
Many times they are put on by ham radio clubs.

shew01 · 04-02-2023, 04:12 PM

Quote:

Originally Posted by nkaminar

Pete, A link would be helpful.

Maybe something like this?

https://www.electronicsfleamarket.com/

Sent from my iPhone using Tapatalk

Paul Bjarnason · 04-02-2023, 09:16 PM

Please explain what a "shunt" is. Since the ammeter has two terminals on it, what would the sources of the to wires going to it be in an electrical system with a one-wire alternator? Perhaps just the alternator output for one and the other the negative terminal of the battery. (My system is 12-volt negative ground.)

Paul Bjarnason · 04-02-2023, 09:19 PM

I just received the ammeter which I ordered from Auto Meter Products. The order clearly states that I ordered a 1.5" voltmeter, but the one they sent me is 2" in diameter. I just sent them an e-mail asking if they really have a 1.5" voltmeter and informing them that they didn't send me what I ordered.

Charlie Stephens · 04-02-2023, 11:43 PM

Quote:

Originally Posted by Paul Bjarnason

Please explain what a "shunt" is. Since the ammeter has two terminals on it, what would the sources of the to wires going to it be in an electrical system with a one-wire alternator? Perhaps just the alternator output for one and the other the negative terminal of the battery. (My system is 12-volt negative ground.)

A shunt is a second wire that bypasses the ammeter. The result is that part of the current goes through the ammeter and part of the current bypasses the ammeter. Here is a picture of the ammeter in my '32. Do to limited space behind the dash in a model A you may need to do the bypass at the junction box on the firewall. Of course the ammeter will read low.

Charlie Stephens

katy · 04-03-2023, 09:36 AM

Quote:

Since the ammeter has two terminals on it, what would the sources of the to wires going to it be in an electrical system with a one-wire alternator?

The ammeter goes between the battery and all the electrical loads (except the starter) including the alternator or generator. 6 or 12 volt doesn't matter.

ModelAArmy · 04-03-2023, 11:46 AM

I had a problem with the ammeter and had a club member direct me to an auto parts store to get a voltmeter. I installed it and it fit perfectly in the dash as the photos show

Paul Bjarnason · 04-03-2023, 01:11 PM

Thanks to all for the good information. I now know what to do. Best. Bj

Paul Mike · 04-03-2023, 01:12 PM

I ran across this some time ago. Westach has a good reputation, but I have not bought one of these. https://www.westach.com/voltmeters

rotorwrench · 04-03-2023, 03:18 PM

A shunt or a resistance wire (the wire is calibrated for resistance by the length using a formula for that purpose), is generally only needed on high amp output system such as an aircraft alternator or starter/generator. The shunt was needed in most of the helicopters I've worked on with exceptions for the small helicopters with reciprocating engines that just used a calibrated wire.

The model A ammeter has a built in bypass strap type shunt since it is such a low current system. Shunts will allow for a sample of the current flow to be taken by a small meter circuit so it won't be damaged by high current flow through the meter. At 15-amps, the little model A meter works just fine unless a terminal nut comes loose.

nkaminar · 04-04-2023, 08:51 AM

Paul, I assume you know how to re wire the car to use a voltmeter instead of an ammeter. But for those who don't know:

A short wire will have to go between the two terminals on the junction box to take the place of the current path through the ammeter. The voltmeter will have one terminal connected to one terminal on the junction box and the other one hooked to a good ground point. Which terminal on the voltmeter will be hooked to the terminal on the junction box and which terminal hooked to ground will depend on whether you have a positive or negative ground. Plus to plus, negative to negative.

David in San Antonio · 04-06-2023, 09:54 AM

Quote:

Originally Posted by gdmn852

Hello, I have both voltmeter and battery condition indicators in my MGB , as previous post mentioned, nice to monitor the electrical system. Mine are vintage Smith’s gauges and are as old as the car 1971 and still do the job.On the battery condition,actually a voltage meter, you can turn ignition on before starting car it will show the charge in battery.

@gdmn852 Voltage meter is battery condition. What is the other gauge? Sorry if I’m confused. Thanks.

03-31-2023, 06:22 PM	#1
Paul Bjarnason Senior Member Join Date: Jul 2018 Location: Annandale, VA Posts: 150	Voltmeter instead of ammeter I installed a 12-volt alternator in my '29 Tudor and would like to have a voltmeter gauge in the stock ammeter location. But, the stock ammeter hole in the dash plate is only about 1.5" in diameter while available voltmeters are 2 1/8". I found a digital voltmeter which is smaller than 1.5", which I can probably make fit, but I think an analog voltmeter (one with a needle) would look better. If anyone has done this, please inform me as to what gauge you bought, from where, and how you installed it. I think I could bore the dash plate out to fit the 2 1/8" gauge, but would prefer one that fits the stock dash plate. Thanks.

03-31-2023, 07:36 PM	#2
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,904	Re: Voltmeter instead of ammeter I did a quick google search for 1.5 inch diameter voltmeter and found this: https://www.autometer.com/1-1-2-volt...075s-elec.html. I did not go further but it looked like there were more. I have a voltmeter but it is mounted below the Model A instrument panel. I kept the ammeter. The voltmeter is handy and my goto meter to assess the health of my charging system and battery, but the ammeter is handy as a backup and to assess the health of my ignition system. With the alternator, after the battery recovers from starting the engine, and the voltmeter goes to 14 volts, the ammeter shows no charge or discharge. That way I know that the battery is fully charged and that it is happy. When I sit at an idle I can see that the alternator is not putting out by the voltmeter at around 12 volts and that the battery is supplying the current to run the car by the ammeter showing a discharge. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 03-31-2023 at 07:43 PM.

03-31-2023, 08:19 PM	#3
Paul Bjarnason Senior Member Join Date: Jul 2018 Location: Annandale, VA Posts: 150	Re: Voltmeter instead of ammeter I just ordered the 1.5" voltmeter from the source you found. Thank you for the tip. Bj

04-01-2023, 01:07 PM	#5
Charlie Stephens Senior Member Join Date: May 2010 Location: Southern California Posts: 7,033	Re: Voltmeter instead of ammeter DUPLICATE post Last edited by Charlie Stephens; 04-01-2023 at 01:11 PM. Reason: DUPLICATE post

04-01-2023, 01:35 PM	#6
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,904	Re: Voltmeter instead of ammeter Sponsored Links (Register now to hide all advertisements) Charlie, The ammeter can be just kept as it is when adding a voltmeter. The ammeter is handy to have in addition to the voltmeter. Hanging below in my my car is a voltmeter, a tachometer, a temperature gauge, and an oil pressure gauge. All nice to have. I pay more attention to the temperature gauge than any other gauge. Second is the tachometer. The original style ammeter is in the usual place. The voltmeter let me know that my alternator failed on one road trip. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

04-02-2023, 07:31 AM	#7
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,904	Re: Voltmeter instead of ammeter Pete, A link would be helpful. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

04-02-2023, 09:16 PM	#11
Paul Bjarnason Senior Member Join Date: Jul 2018 Location: Annandale, VA Posts: 150	Re: Voltmeter instead of ammeter Please explain what a "shunt" is. Since the ammeter has two terminals on it, what would the sources of the to wires going to it be in an electrical system with a one-wire alternator? Perhaps just the alternator output for one and the other the negative terminal of the battery. (My system is 12-volt negative ground.)

04-02-2023, 09:19 PM	#12
Paul Bjarnason Senior Member Join Date: Jul 2018 Location: Annandale, VA Posts: 150	Re: Voltmeter instead of ammeter I just received the ammeter which I ordered from Auto Meter Products. The order clearly states that I ordered a 1.5" voltmeter, but the one they sent me is 2" in diameter. I just sent them an e-mail asking if they really have a 1.5" voltmeter and informing them that they didn't send me what I ordered.

04-03-2023, 01:11 PM	#16
Paul Bjarnason Senior Member Join Date: Jul 2018 Location: Annandale, VA Posts: 150	Re: Voltmeter instead of ammeter Thanks to all for the good information. I now know what to do. Best. Bj

04-03-2023, 01:12 PM	#17
Paul Mike Junior Member Join Date: Nov 2017 Location: Arvada, CO Posts: 28	Re: Voltmeter instead of ammeter I ran across this some time ago. Westach has a good reputation, but I have not bought one of these. https://www.westach.com/voltmeters

04-03-2023, 03:18 PM	#18
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: Voltmeter instead of ammeter A shunt or a resistance wire (the wire is calibrated for resistance by the length using a formula for that purpose), is generally only needed on high amp output system such as an aircraft alternator or starter/generator. The shunt was needed in most of the helicopters I've worked on with exceptions for the small helicopters with reciprocating engines that just used a calibrated wire. The model A ammeter has a built in bypass strap type shunt since it is such a low current system. Shunts will allow for a sample of the current flow to be taken by a small meter circuit so it won't be damaged by high current flow through the meter. At 15-amps, the little model A meter works just fine unless a terminal nut comes loose.

04-04-2023, 08:51 AM	#19
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,904	Re: Voltmeter instead of ammeter Paul, I assume you know how to re wire the car to use a voltmeter instead of an ammeter. But for those who don't know: A short wire will have to go between the two terminals on the junction box to take the place of the current path through the ammeter. The voltmeter will have one terminal connected to one terminal on the junction box and the other one hooked to a good ground point. Which terminal on the voltmeter will be hooked to the terminal on the junction box and which terminal hooked to ground will depend on whether you have a positive or negative ground. Plus to plus, negative to negative. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.