Inliners International Forums General Discussion Electrical Alternator to Ammeter

is this the correct way to connect an Alternator to an ammeter? chevy 235

[img]http://i10.photobucket.com/albums/a143/modiol/Alternator.jpg?t=1178048266[/img]

Is this the early (62-70) GM model??

I agree with walt on the dangers of running an ammeter, If you are going to do it make sure that the meter will register more than the MAXIMUM AMPERAGE OUTPUT of the alternator you are using or the meter itself could (will) start a fire. You should use a volt meter with an alternator.

Walt & Bill are correct.

However; You can get an amperage reading from the Igniton switch line(early GM).

What model (year) is your alternator??

No, the ammeter goes in series between the battery and every thing else. The way you have it drawn, it will only read what the alt charges.

I dont know what year or model my alternator is. I bought it at a swapmeet, it's chrome 65 amp alternator. I'm putting it in my 1948 chevy fleetline.

M;

There's no way we can help you without knowing,what kind of Alternator you have.

Look it up in a Motors Manual at your local Library.

The way mentioned (series) by Walt, Bill & Joe is how your 48 is wired for a Generator. This is okay if your wiring is good.

The drawing you submitted is WRONG. Don't put power to anything, yet.


J;

There's more than one way to measure current flow.

I believe it is a one wire alterntor. I am planning on hooking up:
a wire from the alternator to the ammeter
a wire from the battery to the foot starter
a wire from the foot starter to the other side of the ammeter
a wire from the ammeter thru the fuse box to the constant hot on the ignition switch.

[img]http://i10.photobucket.com/albums/a143/modiol/altamm.jpg?t=1178420692[/img]

No! The wire to the fuse box should be to the same side of the ammeter as the alternator, not to the battery side.

If you have a 65 amp alternator your amp gauge better read at least 75 amps or you will burn it up and possibly the car with it. If you want to use your old wires bypass the amp gauge. The reason for a larger gauge than the rating is many 65 amp units will charge in the low to mid 70s range under the right conditions. I have seen guys try this and when it shorts out the whole wiring harness burnt in just a few seconds setting everything on fire. My advice is don't do it unless you don't care if you burn down your car,

Modiol, The battery + connects to the starter solinoid bat post. Then a 10ga. wire preferrably with fusible link runs from the solinoid bat. post to the + side of the ammeter. This is the only wire that connects to the positive side of the ammeter. The Alternator bat wire (10 ga.) connects to the - or negative side of the ammeter (again a fusible link is preferred). The ignition switch feed and the fuse block feed also connect to the negative side of the ammeter. You really must have an ammeter capable of handling the power of the alternator. I have gone to a volt meter on my cars for the ease of wiring and the safety aspect. S

PS...the diagram in your last post is wrong. The feeds and alternator connect to the same side (neg) and the hot wire from the starter solinoid (battery wire) connects to the positive side. It is the only wire that is supposed to connect to the positive post of the ammeter.

thank you everyone for your input, Im trying to finish up this wiring job.

Would this be correct?

[img]http://i10.photobucket.com/albums/a143/modiol/altammfinal.jpg?t=1178505826[/img]

I want to keep the original look in the interior. The alternator is a 63 amp alternator.

www.watsons-streetworks.com sells a booklet on wiring autos and has the best generic diagram I have seen. Also have a diagram from the January 1983 issue of Hot Rod. They both show and comment that the only wire that attaches to the positive side of the ammeter is the 12 volt positive wire (10ga.) from the battery connection on the solenoid. Also shows the alternator and all feeds attached to the negative side of the ammeter. I certainly agree with you that the voltmeter is by far the best, and easiest way to moniter the charging system. Watsons book shows your way and another way of wiring the ammeter and explains why they are wrong. Sorry I don't have it in hand right now so I can comment on that. I will look it up this morning. Regards, Sam.

Bill is correct!

Most of the time it (ammeter) will be 'peged' & of no use anyway. It will only last till there's a big load (low battery), then It's 'toast'.

I would use a 12V 30A Generator to keep the 'orginal' look. You ONLY need an Alternator if runing A/C.

These (high amp) Alternators are made for cars/trucks or Station Wagons with a lot of electrical acessories (power windows, rear gate) and A/C.

The only (other way) would be to rewind the orginal ammeter to handle the load, which is to costly.

Happy trails.

Thanks Walt. No argument from me either, just explaining it as the diagrams on hand show. There is one thing I do not understand about gens and alternators. Do they put out the rated current, or do they only supply what is demanded by the circuit? S

Dear Sam;

They (both) only put out the current required to maintain the voltage (demands) of the system.

All vehicles today have an A/C option when new and why we have Alternators. Without A/C a Generator is all you need for a 1948 vehicle.

Even with all the lights (& high beams) on, all those circuits pull is around 20 @ 6 volts and less at Twelve.

The exception being;

Say you run out of gas and have to crank it a lot for restart; now your battery is lower than 'normal'. For a minute (or so) this 60 Amp. unit sees a voltage demand and cranks out 50+ amps to make it up. A 30A 1948 ammeter can't handle it and fries. Now; If it 'shorts' in the process it toasts the wireing too; as Bill has mentioned.

Voltmeters are used today as they are NOT in 'series' with the charging circuit and this can no longer happen, which Walt has addressed.

Happy trails.

Thanks John. That is sort of how I expected it to work but didn't have any idea about amp numbers. Sam

thanks for all the tips people, I think i'm just gonna run the alternator directly to the battery and leave the ammeter in the dash (not connected)to look pretty.

What are the pros and cons of using a Hall-Effect ammeter ? I'm a mechanic/mechanical engineer, and I do not understand all of the electronics, but my EE friends say that this is the way to go. They and I would not want to use a direct-reading series ammeter that carries a lot current through the gauge.

Mr. Hoyt;

This is the way early vehicles were built and how the operator monitored the charging system. This worked well for decades until "idiot lights" were used instead. Rarely was the charging circuit fused, but there were/are devices for that.

It also works the same today unless someone adds equipment (like A/C) where it (orginal) no longer can, due to the added power source/drain.

The "hall effect" devices have been used by mechanics to test charging systems W/O ammeters for decades. The one shown is not needed as a Voltmeter allows the operator to monitor charging safely. It's just another 'gadget'.

M;

You WILL need to make other modifications to do that on your 48. Stick with a Generator or use an early GM (30A) Alternator and the (orginal) wiring design is just fine.

Happy trails.

John, I could be wrong but I don't think that the decades old ammeter used to check starter current uses a hall effect sensor. I would have assumed that it was magnetic; the same as your in-dash gauge.

Hoyt, voltmeters are so much easier and tell you all you need to know about your charging system that I can't imagine going through the trouble to add an ammeter to a vehicle.

Jason,

I agree on both points. However, if somebody really wants an ammeter, the semiconductor Hall effect device, similar to the link above, seems to be the only reasonable approach.

When I was earning my living as an auto mechanic over fifty years ago, I remember using the Snap-on magnetic diagnostic gauges that one just held over the battery cable or generator cable to measure cranking or charging current. Thise still seem to be sold by Snap-on, and are not the same as the the newer clamp-on gauges.

For my current project (a 278 cubic inch 1954 Chevy in a highboy) I am using an alternator and voltmeter. As much of an "old school" person that I seem to be, I have no desire to start battling generators and ammeters again.

J;

Okay; "hall effect type" that measure the current flow (charging system) W/O a direct connection. Measuring the starter's 'current draw' has/is done (decades) that way also, but wasn't part of the discussion.

H;

Mr. Modiol wanted to use his (orginal) ammeter built in 1948 and It's dangerous to do that with a 'high amp' alternator. To do this he needs a 30A source, Two of which I provided.

You asked for an opinion on the 'Hall effect' device, which I also provided.

Good luck with your Roadster.

Hoyt, there is another approach. I have a clip on ammeter using an iron cored inductor which can be clipped on the wire. The inductor is part of a resonant tank circuit. As the current increases, the core saturates causing the inductance to drop with a resulting change in the resonant frequency. Signal conditioning converts the frequency to voltage which is displayed as current on the meter.

Interesting comments on this subject in the "Shop Manual" column of the June '07 issue of StreetRodder Magazine. The remarks are attributed to Ron Fransis and discuss rewiring and using a shunt on the ammeter. S

Gentlemen;

It doesn't matter how one monitors the charging system. One can use lights/buzzers a Voltmeter/Ammeter, or any combination of these.

As Walt would say; "make your own decision".

The point that's lost here is that "Hi-Amp" Alternators aren't needed in MOST cases.

From the 30s thru 1954 all Chevrolet vehicles had a 6V 30 Amp system and all was well. With high beams on and the radio/heater the system "handled the job".

When the (early) vehicles are 'converted' to 12V the current requirments drop in half and the (55-61) Generator still can produce (30A) which is much more that the vehicle needs, by almost two thirds.

If one choses to add A/C then the (62-72) Alternator (30A) is way more than enough to; "handle the job".

These "high Amp" units are designed for 'high current dependant' devices, which Commercial vehicles, Motorhomes need and Hot Rods seldom have.

Happy trails to all.

I have found this post most interesting---I have a 52 Windsor and have installed a 6V pos gnd alt, it puts out 37 amps and my amp gauge goes to 50, will it be a problem? It`s a single wire hook-up..................Thanks 52er

Thanks Walt--I was concerned that my guage would be a problem and there could be a fire. Being my alt only puts out 37 amps and the guage goes to 50 I should have some room for any spikes in current. I fused the line on the alt with a 30 amp fuse or should I go higher? Thanks....52er

Dear Lee;

Not at all as; The 37 Amp output is below the 50 It's designed for.

The Alternator will ONLY put out the current required to maintain the system and all the stock items are way below that.

Using #10 wire (feed line) is important though as Walt has mentioned.

Good luck.

John--Walt, I gutted an old reg. and put a double fuse block inside---I took the 10 ga. wire from the arm lead and went to the alt and took the 10 ga wire from the amp meter to the other side of the fuse to complete the circuit---left the old wires on the reg to make it look factory and the fuse is safe from the elements and mechanic mistakes--like myself---just got the dash back in and we have power, but I am not ready to turn it over yet. Want to finish some small hook up`s with the heater and radio---all the dash,brake, turn,wiper all work----the re-wire took some time, but time well spent---atleast I know it`s done right. Thanks again guys....52er

L;

You might consider a 'Group 2' Battery, if you haven't got one yet. There 6V, but have a larger capacity (cranking amps) than the 'Group 1'.

Some of the larger (Chysler products) cars had them & it wouldn't look "out of place".

Good luck.

JOHN, I WILL CHECK INTO THAT---- THANKS

I know I'm late on this, but I just found this thread. If you must have an ammeter and don't like running that kind of power to the gauge, use a remote shunt. Aircraft have been doing it since they had charging systems. I remember seeing some in the VDO catalog several years back (it was for a 150 or 160 amp meter though). If you keep the regulator housing one could easily be hidden in there. You wire the shunt just like you would an ammeter, then run wires to the actual ammeter. this does require removing the shunt from the ammeter itself (most I've seen are just a piece of wire between the posts) which if internal could require a trip to an instrument shop.