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Thread: Issue With Ammeter Wiring

  1. #1
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    Issue With Ammeter Wiring

    So, there is this lovely guide on cj3a.info about how to test your charging system. I figured I would follow the guide to make sure there were no issues there before I replace the battery. Turns out, according to that site, I have an issue with my wiring in the ammeter circuits. Here is the direct quote from the website. "Different voltage readings at the battery positive terminal and the regulator battery terminal indicates a problem with the vehicle wiring in the ammeter circuits." I have a couple questions about this. First, that's kind of vague and I'm still not very sure what the problem is or how to fix it. Second, I asked my father about it, and he thinks this result could be caused by the battery being low (which it is, and it needs replaced). I guess I'm really just asking what my course of action should be. I could replace the battery and try again, but I don't want to put a new battery in if we still have charging issues. Option 2 is to try and figure out exactly what is wrong before I put the new battery in. Only other info I can think of is that the battery terminal on the voltage regulator looked much more rusted than the other 2. Any thoughts? All help is appreciated.

  2. #2
    Super Moderator bmorgil's Avatar
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    I am not sure what the web site wanted from the process. That being said I would try this.

    Start the motor hold the RPMs up to 1700 or so, and put a volt meter across the battery. The voltage should be around 13.8 to 14.7 volts on a 12 volt system and 6.9 volts to 7.5 or so for a 6 volt system. Low voltage indicates a charging system problem. If the Ammeter on the dash is indicating a high amperage to the positive, the battery is drawing maximum amperage trying to charge. It is either low or bad. Take the battery to the parts store and tell them to test it. By far a load test is the best way to judge the condition of a battery.

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    Start the motor hold the RPMs up to 1700 or so, and put a volt meter across the battery. The voltage should be around 13.8 to 14.7 volts on a 12 volt system and 6.9 volts to 7.5 or so for a 6 volt system.
    Well, that was part of the test and I got the voltage I was looking for.
    If the Ammeter on the dash is indicating a high amperage to the positive, the battery is drawing maximum amperage trying to charge. It is either low or bad.
    That's the other thing I forgot to mention, I don't think the actual dash gauge works. It always shows 0 no matter what.
    Take the battery to the parts store and tell them to test it. By far a load test is the best way to judge the condition of a battery.
    I certainly could take the battery to Autozone for a test, but I'm almost certain that it's dead.

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    If you have a trickle charger you can try leaving the charger on the battery for a day. Take it off and check the voltage. It should be over 12 volts. More like 12.5. Then check it periodically and see if that voltage drops. If it does you battery isn't keeping a charge. Sometimes a battery will hold good enough that you can use it as long as you start and run everyday, but won't hold if it sits for a week.

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    Super Moderator LarrBeard's Avatar
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    "That's the other thing I forgot to mention, I don't think the actual dash gauge works. It always shows 0 no matter what."

    You can test the actual gauge with a D-cell flashlight battery and a couple of wires. Get in behind the dash and disconnect all the wires from the ammeter - keep track of where they were connected. Hook a wire to each terminal of the ammeter. Connect the D-cell battery to the two wires. The ammeter is, for all practical purposes, a dead short. A D-cell alkaline battery will drive 5 amps or so into a dead short. With the battery connected to the meter, the needle should deflect up or down off zero. Reverse the wires and the needle will deflect the other way.

    No deflection, bad ammeter. Don't leave the wires hooked up too long, the battery doesn't really like to be stressed like that!

  6. #6
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    It should be over 12 volts. More like 12.5. Then check it periodically and see if that voltage drops.
    It's a 6 volt so I should hope it doesn't read 12.5 volts lol. But once again, I know the battery doesn't hold charge. I have to charge it every time before I start it. Now that I think about it, if my charging system works (which I believe it does at this point) would a fubar battery still not get a charge from it?

    You can test the actual gauge with a D-cell flashlight battery and a couple of wires.
    Thanks for the tip! I'll be sure to try this next time I'm working on it. If the guage is bad would it be a good idea to replace it? Or perhaps it would be better to bypass it in some way?

  7. #7
    Super Moderator bmorgil's Avatar
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    Viper you are on track. The correct voltage at the battery test indicates the charging system is trying to charge the battery. A battery can charge up and hold voltage, but have no current capability. by taking it out and getting it tested you will know if it will take a charge and provide current, or not. A load test is the way to find out. It might be good, just dead. Dead lead acid batteries sulfate and are quickly ruined. You must keep them fully charged. Take the battery in. Since you show 7+ volts while running, the battery is suspect. The Amp gauge may be correct. The battery may not be taking a charge.

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    Super Moderator LarrBeard's Avatar
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    "If the guage is bad would it be a good idea to replace it?"

    Yeah - that would be a good idea. There are only four gauges on that panel, but every one of them monitors something important to either get you where you want to go or to keep from damaging the engine.

    I suspect BMorgil may have hit the problem on the head - you have a sulfated battery that won't take a charge. Pull it and get it tested. Auto Zone would love to test it for free and sell you a new battery!

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    Super Moderator gmwillys's Avatar
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    Baby, non coated Tylenol, one dropped in each cell then charged, can reduce sulfated cells. This is a farmer's trick to help the longevity of a battery, but for whatever reason 6 volt batteries don't live long. I've tried Tractor Supply Travelers batteries, and some of the parts house batteries. I probably need to invest in battery company stocks, or better yet a battery tender.

  10. #10
    Super Moderator bmorgil's Avatar
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    I have been told these are real good products. I have a 12 volt in mine. We have a couple of this brand around. A large USA manufacturer. This link is their commercial offerings for a 50' 6 volt CJ3A. http://www.dekacatalog.com/ Look for a Deka 901MF
    Last edited by bmorgil; 06-21-2020 at 06:06 AM.

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