The Stovebolt Site Forums The Shop Area The Electrical Bay Ammeter vs. Voltmeter

Since I just pulled a bone head stunt and fried my Ammeter, I am wondering what anyone has to say about which is a better gauge to have. I always thought the Ammeter would tell me that the Alternator or generator was working, or measuring the flow of power.

Any thoughts/recommendations?

I prefer a voltmeter

voltmeter is safer

ALL voltage/power leads go thru the ammeter except the starting circuit. The main electrical system is wired thru the ammeter back posts. Because of this, possibility of great harm IF those
screw posts come in contact w/ a grounded wire or wrench to gnd, is the consern safety.
cover the posts w/ some plastic caps.

Your right Mike, think push and flow. The Voltage is the amount of electrical presure and the Ammeter is the amount of current flow. It's fun to have both but if you only have room for one, go with the current flow, it tells you more about what is happening in your electrical system.
Denny Graham
Sandwich, IL

MikeE,

The voltmeter will show you that your system is charging and will show the approximate state of charge of the battery. This is usually enough to make the average Joe comfortable. If you need to see how much current various items are actually drawing then the ammeter is for you. You will probably never ever be able to 'fry' your voltmeter, and being tagged into the system the way it is, you don't end up with one meter passing all the power, which some consider dangerous.

I think this is sort of a personal preference kind of deal!

Stuart

I'm from the old school and always liked ammeters. I liked being able to monitor the level of the charge. I always thought of the voltmeter as being another cost cutting trick on the part of the manufacturers.
However, my '56 had been converted to after market gauges before I bought it. After becoming familiar with it I find that I can still monitor the charging system with a voltmeter. The obvious advantage, as mentioned, is the fact that your entire electrical system doesn't run through the voltmeter as it does with an ammeter.

I'm still not fully converted though. In the '54 GMC I'm planning on running stock gauges. As Stuart said, "....this is sort of a personal preference kind of deal!"

Thanks Everyone, lots of food for thought. I may wire up a replacement Ammeter in the dash cluster and add a voltmeter.

Decisions Decisions!

Again Thanks

I believe some of the above post may not be entirely correct. Correctly wired ampmeters reads the amount of current going into or out of the battery and the service charge for the battery from the altenator/generator. Correctly wired ones don't show the total current draw for the complete electrical system. You have about one in four chances of getting a re-wired one from a PO that is correct. Downside of ampmeters are large current conductors in dash and the problems that could cause. Really nothing to worry about IF the wiring is done correctly. By that I mean things like...grommets when passing through holes, correct wire/fuse size, correct hookups, etc. Voltmeters work just fine and are much less hassle to get it right with smaller wire. In the end it whatever you want.

The only current in a 1946 truck not going through the ammeter should be the starter current.

Baldy, can you point me in the direction of a wiring diagram of a '46 truck? I've checked my references and can't find a drawing with an ampmeter hooked up as you say. All my drawings show the starter and battery on one side of the ampmeter and the electrical system PLUS the generator hooked to the other side of the ampmeter. Thanks

beltfed,

Although I'm not Baldy, I am pretty shy of hair on top! I have enclosed a link to a '46 wiring diagram. You can see it is wired just as described above.

http://chevy.tocmp.com/chevywiring/diagrams/1946truckwiring.pdf

Stuart

Mike your situation mirrors mine exactly. I replaced the ammeter that was not working for some unknowen reason, with a volt meter. The instructions were easy and it went in like a snap.
HOWEVER they didn't tell you what to do with the left over 2 wires from the hot post on the starter and the altenator. I finally discovered by my self that they must be connected together to properly charge the battery. They can be shortened considerably under the hood. getting away from these high amperage wires under your dash. Hope this helps a little bit.

Thanks Atomarc. I have printed a copy of the drawing and will study it plus put it in my reference file. As always, I'm here to learn and by golly it happens more often than not.

Beltfed,

Saying that he only current not going through the ammeter is the starter current is exactly the same as saying that the starter and the battery are on the same side of the ammeter with everything else on the other side.

Atomarc & Baldy, I have reviewed the drawing on the '46. I don't see how one could say that "the only current... not going through the ampmeter should be the starter current". Since the generator and the electrical system are both connected to the same side of the ampmeter and the generator runs things when the engine is running, I can't see your point.

beltfed,

I saw this question coming a few posts earlier. I don't know if I could explain it clearly, but will say this. The starter draws a huge amount of current, so for this obvious reason it isn't wired through the ammeter. The charging system and all the loads in the system are tied together on one side of the ammeter, while the storage tank...the battery, is on the other side of the meter.

I don't know is this is electrically correct, but I visualize it this way; When the rig is started and the charging system is charging, current flows through the ammeter to the battery and the gauge indicates a 'positive' or a charge.

When this is happening, and you turn on your headlights, some power goes from generator to headlights, but some still goes to battery. The needle still shows charge..+, but just a little less +. If you turn on everything imaginable, the system can't supply it all, try as it may. Now the battery helps feed the loads and the ammeter needle swings to discharge, or -.

This is how I understand it...does it make any sense to you or am I all wet?


Stuart

beltfed the guys are on to it mate the main start cables are all that is not fed through the ammeter as the start current is in the hundreds of amps and would cook the ammeter in seconds.the ammeter needs to be connected as per the diagram so as to show both a discharge and a charge state.my view is that a voltmeter is alot safer but as pointed out the ammeter wired correctly with grommets etc is ok,as i have said in preveous threads if you run an alternator that is higher in output than standard or you have a huge stereo or accesories load i would go with the voltmeter.happy truckn p.s the reason the main cables need to be joined if the ammeter is removed is that an ammeter is connected in series and as such the (current) must flow through it where as a voltmeter merely sences or samples the potential pressure (voltage) and therefore is connected in parallel.hope this niether blinds you with science or baffells you with B.S. regards west

Somehow I know we're saying the same thing. As the old saying says, "Same church, different pew". I know Atomarc, Baldy, and now West Aussie are very familiar with electricy and electrical systems. Myself, I have over 30 years of instrumention and process control experience and have rewired a number of cars as I know ya'll have. With that said, maybe we should just move on and save this item for a "bench racing" session. Thanks

After seeing all your comments, I think I am going to relook my re-wire job from a couple years ago. Not that I would have gotten anything confused but just to make sure.

Gazim, your comments are well taken, I am thinking about putting in an add on voltmeter just for grins.

This whole adventure started when I was replacing my fuel gauge and decided to get an improved oil pressure gauge. That way I could get rid of my add on oil pressure gauge. Just trying to clean up the dash area a little.

Thanks again.

Mike, my next project will be to replace the entire gauge setup with a more modern look unit
I now have the speedo and 4 aux gauges. Going to get a quad gauge,speedo and tach mounted up on a alum. piece to fit in. Will let you know if I get everything working again. :hammering:
The volt meter was just a fix until I get the other pieces assembled. I do notice that the pieces I want Don't have a ammeter, only volt meter

Gazim,

Sounds great! And high tech as well. I am still basicaly original. Don't know what I would do with an accurate speedo, then again I only go about 45!

Well, I'm no speed demon but my speedo reads about 6mph to fast so I feel like I am going faster. I think I can get a new gear for the muncie, but what the heck, I'd rather get a new rear end gear. 4'11 is kinda low.