Aaron76

I am installing new gauges in my car and replacing the ampmeter with a voltmeter. Can I just connect the two leads that went to the ampmeter togeather and tap off this connection for the voltmeter or should I wire it different.
Thanks.

GrandSportC3

You have to wire the voltmeter different.. Both wires on the ammeter have 12 Volt.. The Voltmeter has to be connected to +12 Volt on one side and ground to the other side..

Larry B.

They are wired differently as stated. Ammeters are in and relate amps being used either way+ or - . I like ammeters better personally as you can tell the condition of the battery (rate of charge vs. voltage) a lot easier. Volt meters tell you nothing about the battery, only the voltage comming from the regulator.


[Modified by silvervetteman, 12:28 PM 2/21/2003]

pws69

To replace the Ammeter with a Voltmeter, do the following:

Solder the two wires you take off the Ammeter together and tape up the junction to be sure it won't short or get frayed.

Now you need to run two wires to the Voltmeter. One to a GOOD ground (connects to Negative - terminal on Meter), the other to a SWITCHED (only on when the key is on) +12V (connects to the Positive + terminal on Meter), (preferrably to a MAIN trunk - to ensure accurate readings - you don't want a "small" wire that's way down the line from the battery.

GrandSportC3

That's the way that I did mine :yesnod: :yesnod:

mrvette

Connect the two together, and then also to the positive on the voltmeter....that gives you a good referance, same as the red wire of the regulator of the alternator....the negative of course goes to groung...duh....

Silver, I don't know how your understand your electronics/electricals...but a voltmeter does rely on only one assumptiion, that your wiring is good....
yeh, it's POSSIBLE to have say 14 volts on the system, and the battery terminals so bad they will not charge the battery correctly....but I say the opposite is more true...the car will NOT start...period....

within a very few tenths of a volt...I mean typically 3 tenths...that's .3 volt, the running voltage at a proper alternator output should be the same as at the battery, same as the radio, say....or even the heater motor when on high...now that's the standard I have on MY car, and I rewired it to fullfill that standard, anyone else can tolerate what they will off old stock wiring/gear....
but the facts of the matter are that a voltmeter is much more useful than any ampmeter in determining if the electricals are operating up to snuff....

not trying to pick a fight Silver, but please.....I been there done that too much over too many a year/decade to tolarate any differance of opinion...

GENE

pws69

Gene,

I don't believe your method is a good one as it will drain the battery!

The Ammeter is a "series" device that does not draw a load.
There is ALWAYS 12V present in the Ammeter wires. Just press the brake or turn the headlights on with the ignition OFF and watch the Ammeter.

A Voltmeter, on the other hand, DOES draw a load and is connected to a SWITCHED source. So if you just connect it to the Ammeter leads that you tie together, you will introduce a constant load.

Paul

mrvette

pws69, you are RIGHT, I freaking BLEW it...so tape the two together, and find a switched +12 volt source...I used the radio wire, I think...it would be fine anyway....sorry....my bad....

GENE :confused:

Larry B.

mrvette. I completely understand how the system works. Let's say that your battery is always being charged. with a volt meter you only know that the regulator is above batter voltage.. That's all, without the ability to know the rate of charge. I agree that if there is a problem that could be mis leading. but then if you have a battery that is always accepting say 30 amps, you could suspect a bad battery. Volt meters on the other hand may lead you to a bad regulator. Each one has it's plus's and minus's (pun intended) :lol: I just prefer ammeters.

mrvette

Silver I am POSITIVE my voltmeter has more + attributes than your - ampmeter.....i'ts all in how you read the silly things....thing is I find the way the typical GM ampmeter is wired in series with the regulator sense wire, the readings can be very misleading. ...and you got NO way to know if the system is good seen it too many times in buddies cars and my own...unfortunately....since I have redone most electricals in my various hotrods...and using voltmeters exclusively....well I have no troubles...vs my negative experience with original amp meters....

pays your money takes your choice.... :D :D

GENE

Ganey

When I bought my 77 called my CE (Customer Engineer Main frame computers, one of the best in the world) to find out which was better.
The voltmeter.

:cool:

Was used to ampmeter & ready to change.

norvalwilhelm

I believe an ammeter doesn't care about the condition of the battery and is in series with the output of the alternator. It reads the output of the alternator. If the alternator is putting out 50 amps but your power requirements are 60 the alternator stills just shows the 50 amp output, not that the battery is slowly loosing 10 amps. The battery could be going dead and the gage still shows a positive charge.
Now a voltmeter only reads the condition of the overal system. Regardless of the power drain it reads the overal condition. It doesn't care if you are drawing 50 or 60 amps just if the system is alive and health. As long as the voltage is reading about 14 volts while running the charging system is alive and well. If you overdraw the alternator the voltage will drop throught the system. Race cars never run ammeters but everyone runs a voltmeter.

Aaron76

Thanks for all your help that cleared it up for me
I will be sur to post some pic's when it is all done.
TTFN