what is correct wiring for a 12v system

F

forte

Junior Member
We have a '53 flathead in a '40 with the help of Ford Barn. We are using a single wire alternator, 3 pole solenoid , starter, battery neg. grd. , ammeter +- terminals, & a coil. No regulator. Using orig. ignition switch and push start button.
 
This is basically how my 1 wire is hooked up.
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Unless you got something special; most of those 1 wire alternators are 100 amps or so. I wouldn't run them thru the stock ammeter.
 
You can use a stock 6v harness for 12v. Only thing you really need to pay attention too is charging/gen/"regulator" - alternators have built in voltage regulators, ignition (coil) components, lights, and gauges.... the harness can handle it no issues.
 
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You could smoke your amp gauge. Think most stock amp gauges go to around 20/30 amps, with a alternator and components you add, you could exceed it quick.. I like amp gauges but some do not. 6volter guy.
 
If the amp meter is a wire through a loop style it will only peg.
The wire is what you have to fry and start a fire for bad things to happen.
If it´s a post style amp meter they are not very good at taking abuse...rebuilding them with an external shunt is the best way to go if you want to use them.
 
good info.


I ran my 6v wire the opposite direction through the loops and the the meter ran negative. Loops must run on field energy. Had to reverse the wire loop to get it correctly read.




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In a typical application, the ammeter is placed between the battery and the solenoid. It indicates if the battery is draining or being charged. So the amperage it sees is a lot lower than what the alternator can put out to run the rest of the devices which are on when the engine is on.
 
You should be very careful running 12v through an original Ford ignition switch. The original switch was only designed to operate the ignition, not added accessories like radio, heater, etc.
 
Juergen said:
In a typical application, the ammeter is placed between the battery and the solenoid. It indicates if the battery is draining or being charged. So the amperage it sees is a lot lower than what the alternator can put out to run the rest of the devices which are on when the engine is on.
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Yep, should be looking at current flow to and from the battery.
 
Alternators don´t like being disconnected while running so i wouldn´t put anything you can disconnect between it and the battery...
Wiring should be able to handle what the alternator puts out with 37A being in the same range as stock.
 
Most amp meters only register the load on the system. If there is no load then it will stay on the center line. A person should know what the alternator output is for their unit. Many of the older ones were from 35 amps up to around 42 amps. A D'arsonval type amp meter with two terminals can get damaged if there is ever a short in the wire from the alternator to the frame anywhere. If a person calculates the proper size and length of wire, the wire can be used as a shunt for the amp meter but I like the purpose made shunts better. A lot of cheap units have the shunt internal to the meter.

The aircraft I work on have a battery switch to access the battery to the buss as well as an alternator switch to turn the alternator on and off. A person can see if their alternator is working by shutting off the battery switch momentarily to see if the alternator stays on line. If it shows no indication of electrical operation when you shut off the battery switch then the alternator isn't charging. It doesn't hurt anything as long as you don't leave the battery off for more than a few seconds. It's just s momentary check that some pilots do. Most of the later models have a low voltage warning light now days that will tell you if it's charging or not. Personally, I like a volt meter better. If it shows near 14-volts then the alternator is definitely working. If it only shows battery voltage then the alternator charging system has a problem somewhere or the load is high.
 
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rotorwrench said:
Most amp meters only register the load on the system. If there is no load then it will stay on the center line. A person should know what the alternator output is for their unit. Many of the older ones were from 35 amps up to around 42 amps. A D'arsonval type amp meter with two terminals can get damaged if there is ever a short in the wire from the alternator to the frame anywhere. If a person calculates the proper size and length of wire, the wire can be used as a shunt for the amp meter but I like the purpose made shunts better. A lot of cheap units have the shunt internal to the meter.

The aircraft I work on have a battery switch to access the battery to the buss as well as an alternator switch to turn the alternator on and off. A person can see if their alternator is working by shutting off the battery switch momentarily to see if the alternator stays on line. If it shows no indication of electrical operation when you shut off the battery switch then the alternator isn't charging. It doesn't hurt anything as long as you don't leave the battery off for more than a few seconds. It's just s momentary check that some pilots do. Most of the later models have a low voltage warning light now days that will tell you if it's charging or not. Personally, I like a volt meter better. If it shows near 14-volts then the alternator is definitely working. If it only shows battery voltage then the alternator charging system has a problem somewhere or the load is high.
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Didn't have to worry about all that stuff with my old J-3 Cub :D
 
34PKUP said:
My 60 amp alternator using an induction/loop amp meter has never even come close to "*******".
Is this just a theory ??
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Sorry for noot being clear...
If you run more amps through a loop style then it was designed for it will peg...no damage done.
A post type will burn out if overloaded for more then a very short time.
 
Going back to your diagram, unless the alternator is faulty (say a shorted diode), you will never see a discharge as the alternator should only produce current in the right direction. Then with the engine running and the alternator not producing enough current, the battery will supply the rest and you will not notice it. You are only measuring alternator output, not battery condition or vehicle load. You need a voltmeter or ammeter at the output of the battery to determine battery condition.
 
Juergen said:
Going back to your diagram, unless the alternator is faulty (say a shorted diode), you will never see a discharge as the alternator should only produce current in the right direction. Then with the engine running and the alternator not producing enough current, the battery will supply the rest and you will not notice it. You are only measuring alternator output, not battery condition or vehicle load. You need a voltmeter or ammeter at the output of the battery to determine battery condition.
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Agree. Ammeter should be in wire from solenoid battery connection to the fuse/breaker panel. A volt meter is a great addition to keep track of generator or alternator function.
 
I have a 60A alternator. And put a voltmeter in the circuit. And reversed the directon of the wire goes through the stock amp meter.
 
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