As advised I swapped in a 12v Volt Meter (gauge) in place of the ammeter on my '57 Studebaker Silver Hawk as I have an alternator. I bought 1 direct from Auto Meter, I took the 2 fat wires (red & black) off the ammeter and put both on the Positive post of the voltmeter, and grounded as it said. So my question is my volt meter shows 12v all the time instead of off/on with the key. Is there any significant draw through the volt meter? I could add a toggle switch on the ground wire. It's a perfect fit in place of the original gauge after removing the light socket and is beautifully lit by original bulb. Terminal posts are in correct location and I could probably install the bezel off my dead fuel meter to look better. Miles
Most ammeters are connected between the Battery/Starter feed and the Ignition switch so it will always be live. Connect those 2 [or 3] wires together using a terminal block or solder together [blue circle] Then take the voltmeter 12v+ feed from the switched side of the ignition switch [blue arrow]
I'm not using the ammeter, have been told by several people can cause fire under dash. Alt is 1 wire direct to batt via 80A fuse.
A moving coil voltmeter (what you have there) is a very high resistance, low current meter. It does not draw any real significant current if left on , especially if you use your car weekly or more. If you wanted it to come on with your ignition, leave the 2 ammeter wires shorted (but insulate them from the ch***is of course), and run the positive wire from the voltmeter straight to the "Ignition" terminal on your ignition switch, or any part of the switched ignition circuit. Don't forget that it will only show the voltage at that point in the circuit, but if you have good connections and wiring, the difference at various points will be minimal.
You can make a byp*** "shunt" using 2 x Vishay diodes, and the ammeter will function like normal until the current exceeds the ammeters capabilities [then the diodes open and flow the excess] And if the ammeter totally Chernobyls itself ,the shunt won't leave you stranded on the roadside I've done this mod on several cars where we don't want to butcher the dash [and still want fully functional gauges]
It should not consume a lot of current, but even so, it does it 24/7 if left on 24/7. Wouldn't expect problems in a daily driver, but why build in potential problems when you don't have to? Connect it to a source only hot with ignition on and you've prevented any issues.
To answer your question a volt meter typically has an internal resistance if about 1000ohms That would draw about 0.012 amps It would flatten your battery in about 3 years if left on all the time.
Like said connect the two wires that went to the amp meter together and tape up. Then connect the positive side of the volt meter to the ignition side of the key switch and ground the other side. How about a picture of your Stude Hawk?
Take the 2 wires that travel from the alternator thru the firewall to the ammeter (now voltmeter), back out the firewall to the battery and replace it with a wire that does not travel a long distance and thru the firewall 2 times. That is a big part of why fires are a concern, long runs and old connectors. To 'power' the voltmeter, either run a fused wire from the battery (always on, not the way OE does it) or from the On terminal of the ignition switch (On when car is awake).
Amp meter are constant power. Volt meters use switched power just like fuel, temp, gen does in the dash cluster.
Snagged from autometer instructions posted on an OT board. https://www.americanmuscle.com/autometer-volt-install.html The instructions are quite clear if you read them rather than ***ume or worse yet listen to what the spit and whittle club says. The voly meter works on switched power with a hot wire from the switch and the ground wire. Ammeter survival depends 75 on the extra loads that you add to the system. The more things that you add that draw power the harder it is on the ammeter. No extra load from what it left the factory with shouldnt be a big problem.
Thanks, the answer I was looking for. The modern radio will kill my batt faster keeping station memory than my volt gage. Now I can put my Speedometer back in, working through that hole. Miles
Unless you are running a big amp most modern transistor radios don't draw near the power that the tube type radio did. Check the specs on the unit you bought as far as amp draw. you don't draw much through a 5 or 10 amp fuse.
Oh, Yessir I can read and did read but my under dash looks like The Old Spaghetti Factory. Anything to tidy up, such as stacking 2 heavy wires on a gauge stud instead of adding more taped trash under dash..... So many things have been added then removed since that car was new, wire taps seem to be a favorite on my car.
I love a Spaghetti Western. Everything under the bonnet has new wiring. I am an SDC Member and a Forum user, but have found HAMB people respond faster.
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