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Title: 12v Volt Meter Using 1 Wire Alternator
Description: how to hook up?


buck toenges - September 5, 2009 01:23 PM (GMT)
I have a 1 wire alternator set up for my '53 cj3b. It seems to work well except my volt meter isn't responding. I don't know if it because i haven't "excited" the alt enough yet rpm wise or I don't have the meter hooked up right. I have the red wire from the circuit breaker on the light switch hooked up to the meter on the driver side and I have a wire from the battery side of the solenoid to the passenger side of the meter. Any ideas?
Thanks,
Buck

Lawrence - September 5, 2009 02:40 PM (GMT)

Don - September 5, 2009 02:55 PM (GMT)
QUOTE (buck toenges @ Sep 5 2009, 09:23 AM)
I have a 1 wire alternator set up for my '53 cj3b. It seems to work well except my volt meter isn't responding. I don't know if it because i haven't "excited" the alt enough yet rpm wise or I don't have the meter hooked up right. I have the red wire from the circuit breaker on the light switch hooked up to the meter on the driver side and I have a wire from the battery side of the solenoid to the passenger side of the meter. Any ideas?
Thanks,
Buck

[/QUOTE]

If it is a volt meter and not an amp meter, then one wire to the meter should be a ground (negative) wire and the other wire connected to a hot (positive) wire. You'll have to look at the back of the meter to find the + and - sign.

Keep us posted


elawson - September 5, 2009 03:15 PM (GMT)
Where is the alternator output wire connected?

Eric

buck toenges - September 5, 2009 11:24 PM (GMT)
The wire from the alternator goes to the circuit breaker on the light switch. I do notice when I connect the other wire to the battery side of the solenoid I hear a "clicking" sound in the volt meter. If I hook up the wire directly to the + post of the battery I don't hear it. I am thinking since I hear the clicking that I probably have it hooked up right. Since I don't have the radiator hooked up yet I haven't really allowed the engine to rev up to see if that doesn't excite the alternator. I have read the article about the lamp light and I think that is what I am using the volt meter for since I am using the old style gauges and don't have a charging light.

Should I use a different style gauge? Will a volt meter work or should I use a amp meter?

jeeper50 - September 5, 2009 11:49 PM (GMT)
I'm using a amp meter on my 6v one wire setup.

elawson - September 6, 2009 12:46 AM (GMT)
A automotive volt meter when it is not connected, should have it's needle resting at one end of it's scale, just like the oil pressure gauge does when the engine isn't running. Usually the volt meter will read, at the high end of the scale, a few volts above 15 volts

An automotive amp meter will have it's needle sitting in the center of the scale, and can move left or right of center. I'll often see 30 0 30, 40 0 40, or something similar on the scale.

This above method is correct about 95% of the time. If you're not sure about the meter type, I can go through how to safely test a meter to determine if it is an amp or volt meter. Connecting an amp meter as if it were a volt meter will result in sparks, possibly some "not associated with Sunday School" words, a ruined amp meter and, if you don't get things disconnected quickly enough, ruined wiring (or even a fire in the wiring).


IF (A BIG, HUGE, IF) the meter is a volt meter.....

The volt meter only needs a few thousandths of an amp to operate, so the wire used to hook up the volt meter doesn't matter as long as the wire is insulated and is safe from having the insulation rubbed off the wire. I usually use #14 wire, because I have lots of that stuff on spools. Other wire sizes will work well too.

A volt meter measures the difference in voltage between the two places you have connected the two wires that go to the volt meter.

The way you are describing how you have hooked things up, you have one side of the meter going to +12V (the battery solenoid terminal), and the other side of the meter also hooked to +12V (the terminal on the light switch. Since the two terminals both have +12V on them, the meter will read zero.

Before you go on, MAKE VERY CERTAIN you have a volt meter.

One wire from a terminal of the volt meter should go to the Jeep's body. If you look at the terminals, one or both should be marked. If both are marked, you should see + and - signs. If only one terminal is marked, that's OK as the unmarked terminal is the opposite of the marked terminal.

If neither terminal is marked, that's OK too. To determine + and - of the meter on your own, just hook one volt meter terminal to the + terminal on the battery and the other terminal to the - terminal of the battery. If the meter reads 12V or something close, mark the meter terminal connected to the + side of the battery as + and the other one is minus. If the meter tries to read backwards, the + terminal of the meter is connected to the - terminal of the battery.

Anyway, the minus terminal of the meter connects to the Jeep's body.

A good place to connect the + terminal of the volt meter is to a place in the system that has +12 volts controlled by the ignition switch. Just follow the wire from the ignition coil back towards the ignition switch. If the wire goes directly to the ignition switch, just connect the volt meter wire to the terminal on the coil and you're done.

If the wire from the coil goes to a ballast resistor (usually some sort of ceramic looking device with two terminals) follow the wire from the ballast resistor and make sure it goes back to the ignition switch. If that wire does go back to the ignition switch, just hook the voltmeter wire to whatever terminal goes to the ignition switch.

If all else fails, you can stand on your head and connect the volt meter wire to the ignition switch. In this case, connect the volt meter to the terminal that has the wire that goes through the firewall to the ballast resistor or the ignition coil.

If you have it hooked up correctly, the meter will read 12V as soon as you turn on the ignition key to "run" , and will drop to zero when the ignition key is turned off. There really isn't any need to start the engine unless you also want to check that the alternator is really charging. If you want to do that, you'll see the volt meter jump from +12 V to anywhere between +13 and +14 volts when you rev the engine.


Having said all of that, you can just leave the volt meter connected to the light switch. If you do that, I'd suggest you put a fuse in line with the wire just in case the wire somehow has it's insulation worn through and a short occurs. Also, the volt meter would read all the time. As I said earlier, the voltmeter doesn't consume much current, so it should not drain the battery enough to worry about unless you leave the Jeep sit for several weeks without starting it up.

As you might guess, I prefer to connect the meter so that it only reads when the ignition switch is on.






buck toenges - September 8, 2009 03:00 AM (GMT)
Thanks for the info on the volt meter. Now how would I hook up an amp meter? Looks like I have a power lead from the battery to one side of the switch and then have a lead from the one wire alternator to the other side of the switch?

On the alternator I have a lead from the + side of the battery to the alternator via the screw that is located in the 10 o'clock position. I also have the one wire lead coming from the same 10 o'clock position. This wire is the one that hooks up to the batt side of the ignition switch. Is this correct? The only reason I asked this is because I found a amp meter in my box of stuff and I don't see anything on the cj3b web page that addresses it.
Thanks,
Buck

elawson - September 8, 2009 05:11 AM (GMT)
An amp meter measures current flowing through a wire, so the amp meter must be placed in line with the wire. One way to do it is to cut the wire--you'll now have two ends of the wire--and connect wire end A to one terminal of the meter and connect wire end B to the other terminal of the meter.

It's hard to say exactly how to hook up the amp meter because the wiring has usually undergone many modifications.

So, here's some generalities.


Basically, one terminal of the amp meter connects to a wire that goes to the positive terminal of the battery. This wire can go directly to the battery, or it can connect to some point that is equivalent to the positive terminal of the battery. This is point will be one of the large terminals on the starter solenoid, or one of the large terminals on the foot starter switch. The terminal you choose on the starter switch or solenoid will be the one that has the big wire that goes back up to the positive terminal of the battery. While you can connect to either end of the positive battery cable, you don't want to change where either end of the battery cables connects. The starter can demand more than 100 amps and an amp meter that can handle that amount of current often won't have any noticeable indication for the currents normally encountered in most charging systems.

Connected to the other terminal of the amp meter will be two wires. One of the wires connects to the alternator output terminal. The other wire will be the one that connects to the rest of the Jeep's electrical system. The wire that goes to the rest of the electrical system is often the wire that goes over to the light switch, but beware of any modifications to the electrical system.

The idea is that you want to meter the current going into or out of the battery, but not the current that the electrical system is demanding from the alternator. This way, the meter will show if the battery is being charged by the alternator, or is being discharged because the alternator has failed. If you were to meter everything, the meter would always be showing some value and the "0" reading is good would not apply.

It is very likely (Maxwell's maxim says that Murphy was an optimist) that the meter is connected backwards. The normal arrangement is that a meter indication to the right of zero indicates the battery is being charged and an indication to the left of zero indicates that the battery is being discharged. If the meter does read backwards, just swap ALL of the wires between the amp meter's two terminals.


It is possible more stuff has been added to the electrical system than was installed at the factory. If this is the case, and you don't feel like connecting the extra wires to the light switch, you can connect the extra wires to the amp meter terminal that has the two wires.


One other thing that is worthwhile and might save you from an electrical fire is to install a fusible link wire. This is a special wire that will melt open under extreme current demands. The fusible link wire is usually 4 wire sizes smaller than the wire you're trying to protect, so if you have #10 wire going to the amp meter, you'll need #14 fusible link wire. #12 wire would be protected by #16 fusible link wire, and so forth. This isn't a perfect solution, but it is much safer than nothing at all.

The fusible link wire should be connected in line with the wire that goes to the amp meter terminal with just one wire. Since you want as much wire protected as possible, you'll want to install this fusible link wire at the point where the wire to the amp meter connects to either the battery or the starter switch/solenoid.


After doing any electrical work I check to make sure I didn't cause a short circuit anywhere. To do this, I take a test light and connect the wire to the not yet reinstalled battery cable, and touch the test light's tip to the positive terminal of the battery. If everything in the Jeep is turned off, and there are no short circuits, the light will remain off. If the light comes on, either something was left turned turned on or there is a short circuit. The lamp will limit the amount of current to a safe value, so you can leave the lamp in place while you look for the problem.

If the test lamp never lit up, or you got it to quit lighting up, you can then connect the battery cable directly to the battery and make sure the amp meter is working and reading correctly.





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