The Stovebolt Site Forums The Shop Area The Electrical Bay Ampmeter 49' 1/2 ton

I am changing back to an ampmeter from a voltmeter. Where is the best place to wire it into the wiring harness? I was thinking between the alternator and the fuse box. Also' it is now a 12 volt system. Will this present any problems for the ampmeter? Thanks to all.

My ammeter is wired straight off of the ignition switch with the switch straight off the battery. If you have any devices between the ammeter and battery they could pull current and it would never show on the ammeter.

Here is how to wire the charging system into the ammeter.

http://chevy.tocmp.com/1942_47shop/4247csm1208.htm

And here is an overall wiring diagram. It's not for a '49, but it's pretty close and will give you a general idea of how to go about doing it right.

http://chevy.tocmp.com/1942_47shop/4247csm1232.htm

and here's a better version:

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

I guess a better question would be where to wire into the system with a modern (Approx. 1980) GM alternator. Thanks to all.

You'd be better off with the voltmeter, an original ammeter would sometimes be pegged by the alternator and the heavy wires need to go through the firewall twice with the chance of shorting. It can be done, but the voltmeter will give just as much information with a lot more safety.

Actually....an ammeter is the more accurate measuring device because it tells you not only which direction the current is flowing...ie into the battery or in the case of discharge flowing out of the battery...(which means your electrical load is greater than the charging system can overcome so, some some current is being borrowed from the battery) and in what quanity.

By contrast a volt meter just measures the amount of voltage or pressure behind the current. A volt meter does not tell you the volume of current being used and where it is coming from or going to.

The amp gauge requires that the heavy current travel thru the amp gauge in the dash on the way to the battery. With the introduction of alternators charging systems became more reliable and could easily keep up with the electrical load so the switch was made to volt meters which allowed the use of smaller wiring.

Many industrial applications today still use amp gauges in part so they have a way to measure the volume of current being used. It is the amps that actually do the electrical work.
The volts is equal to the pressure behind the current.

Thanks Randy

No argument that the ammeter is the only way to quantify current, but in a vehicle the voltage will tell you IF you are charging or discharging by being either greater or less than around 12.7 volts, right? I was addressing the fire safety issue.

I understand both points of view. Right now I have an original ammeter and will probably go that direction. Plus I have not found any place that sells voltmeters with the original decals. I guess I still need to know where to wire it into a 12 volt system with a newer style alternator? Thanks to all.

With a single wire alternator, run that wire, along with the wires that power the light switch, ignition switch, radio, heater, etc.(about every thing except the starter), to the ammeter. Run a wire from the starter lug that attaches it to the battery to the other terminal on the ammeter.

The alternator has 3 wires. Heavy duty wire goes from back of alternator to battery. 2 wires plug into top of alternator. I think 1st one (light duty) goes to igniton switch, and second (medium duty)goes to fuse box as the main power source, athough I am not positive. Like I said before it's a GM alternator from approx. 1980.

The heavy wire would go to the ammeter and the other terminal of the ammeter would go to the lug on the starter that goes to the battery. The medium duty wire is probably a sense line. Look at Mr. Horvaths schematics, a search on alternator convesion on this site should get it for you.

Baldy:

A fusable link (or 2) on the Ammeter will prevent any sort of fire or burnt wiring from a faulty gauge.

Alan Horvath has a step-by-step procedure sheed regarding the use of fusable links that is very helpful.

So the ammeter is connected to hot battery power all the time or does it connect to on/off side of the ignition switch.

Thanks to all.

WHY ?????
YES the HOT 12V and high amperage is present in the cab all the time. CAP those posts on the back of the amp gauge for safety !!!!!
First a 12v ampmeter doesn't run the 6v one and may cause you problems. Running a resistor is not the way to handle that.
Note:: NOT all alternators run three wires, you can get them w/ only one wire. There are reasons for having both. Me, I like the three wire better. There are different ways to wire each. If you have a three wire, it is a good idea to run an idiot lamp in the cab dash.
The BIG FATTY wire usually comes from the batt +12v post or you can run it directly off the starter +12v post to the ampmeter plus side. The ampmeter neg side BIG FATTY wire goes to the key switch...........
Ampmeters are a good way to monitor the voltage system while the engine and any electrical systems are in use. You have to wire the ampmeter w/ a BIG wire, both 'in' and 'out' (to the key switch. Everything electrical MUST run thru the ampmeter, so the operator can see the charge rate. This means depending on your electrical accessories and the way in which you have them wired, your key 'out to accessories' should go to a fuse panel, then to the accessory. If you run lots of accessories (or plan to), having that kind of amperage inside the cab of the truck is old school thinking. It is somewhat unsafe to the modern way of wiring w/ relays. Relays allow the 'big' wires close to where they should be located, thus giving those accessories the full power for functional operation. Smaller wires trigger the relay (on- off) from the remote truck cab.
((( Running EVERYTHING thru one wire to ALL your electrical compoments is not really the safe way, The ampmeter way.)))
http://alanhorvath.com/54chevy/mad_electrical.php

one and three wire alternators:
http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=3;t=001849#000000

http://www.tr6web.com/Documents/tr6/meters.html

http://pweb.jps.net/~snowbum/amp&voltmeters.htm

Dispite where this info comes from... apply it to stovebolts cause it's all the same. 12-14 volts 'in and the rate of amps out'. The reference to airheads means an older BMW boxer motorcycle, but again the info is ALL the same and APPLIES to our situation. substitute stovebolt for airhead.

It looks like you have many responses to this question and for some reason you have your reasons why you want to cross back to the ampmeter.

my .02 and it's your truck not ours.

DO as you please.

I would love to keep the voltmeter in the truck. I personally like them better. Is there a place to buy a voltmeter that fits into, and has the same decals as the other gauges for a 49' 1/2 ton? Right now the voltmeter has been adapted to fit in with the current gauges, but looks out of place.