Turn ammeter into a voltmeter?

[BruteForce]

I like the look of the original gauges. But sooner or later, the ammeter has to go (even though mine works fine) and get replaced by a voltmeter. Has anyone replaced the guts of the stock ammeter with a voltmeter, so it looks just like the ammeter but is a working voltmeter instead?

[Bullitt-]

It appears that the ammeter could actually be converted to a voltmeter with the addition of a shunt to the circuit....Any EEs out there to figure this out?
http://www.citycollegiate.com/galvanometer_XIIa.htm

[BruteForce]

I seem to recall that an ammeter is, internally, just a voltmeter measuring the voltage drop across the bus going between the terminals. So, with a bit of electronics, it should be convertible.

I intend to upgrade the tach, so at that time I'll investigate. I have a friend who knows electronics, perhaps he can dude me up a circuit. It should be a fun little project in any case. If I'm successful, I'll report back here on how to do it.

(Since I'm installing an MSD ignition, the factory tach won't work without the $50 8920 "tach adapter". But I can modernize the tach electronics for $75 and not need the 8920, sounds to me like a better deal.)

If anyone has a sacrificial old e-body ammeter they don't mind getting rid of, I can get started on it now!

[71 DEPUTY]

can't use the existing two wires to the amp meter cause they are powered all the time from the battery.

volt meter measures when the power is on- like from the ign. source.

if you put a standard volt meter in your car and use the existing amp meter connections ( both the red and the black bolted and insulated together ) you will eventually kill the battery as it is drawing power all the time!!!

[BruteForce]

I agree. The existing connections would have to be removed, and instead the voltmeter attached to ignition power.

Is the ammeter a bimetal strip that turns when heated, or is it a coil moving to/from a magnet?

[71 DEPUTY]

what happens in a nut shell is this....

when current is drawn thur a wire it creates a magnetic field- more current- larger field. needle in meter deflects either way when current flows either way.

in the amp meter there is a small steel bar inside that the mag.field radiates out from!

[BruteForce]

Oh crud, sounds like it isn't modifiable into being a voltmeter.

[MJS73]

I've been meaning to ask this question, too.  I just sent my gauges out to Red Line Gauges to be re-furbished, add their oil pressure gauge and change the ammeter to a voltmeter.  The mechanic that pulled the gauges asked for further (or better) instructions on what needed to be changed.  So, how do you go about wiring a voltmeter in a '73 Challenger.

Mike

[nivvy]

All you have to do the the ammeter guage wire on each side is butt them up together and be done with it!!! the just wire up the voltmeter.... 

I did it and it works fine....

[MEK-Dangerfield]

All you have to do the the ammeter guage wire on each side is butt them up together and be done with it!!! the just wire up the voltmeter.... 

I did it and it works fine....

   


  If you connect those heavy red and black leads together, you can use that junction for your voltmeter. One wire would connect there, the other to ground. Just make sure when you connect the heavy red and black wires together with your voltmeter, you insulate that connection BIG time. You don't want that baby touching the dash frame.   


  Mike

[BruteForce]

I guess the next step, since the ammeter guts don't appear to be convertible, is to get an auto dash voltmeter, pull out its guts, and schlep it into the dash cluster and doctor it up so it looks like the stock ammeter.

Anyone got a car dash voltmeter, any make, laying around they want to get rid of? My bronco voltmeter looks like just the ticket, but I still need that one for my bronco :-)

[MJS73]

Red Line Gauges sells a voltmeter that looks like the factory gauges.

Mike

[LAA66]

Red Line Gauges sells a voltmeter that looks like the factory gauges.

Mike

 
 I was going to mention that just forgot the company name. They will reconfigure yours for around $100 also.

[71 DEPUTY]

GO HERE FOR MORE INFO!!!!!  http://www.egauges.com/ATM_Tips.asp?TipPage=voltmeterammeter.htm

VOLT METER NEEDS A SWITCHED POWER SOURCE!

[BruteForce]

Thanks for the pointers!