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alternator overcharging

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  • studevic
    replied
    hello all, i have solved the overcharging problem at last , i was nearly ready to give up, anyway with forum help i traced the field wire back from the alternator and found it was connected to the battery side of the starter solenoid so it was getting power all the time and overcharging ,plus it has cooked the battery. the wire on the field side of the regulator was not connected to anything on the engine , anyway i have sorted it out and now the car is able to be driven , thanks again for all your help , cheers from roger

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  • Hallabutt
    replied
    Don't discount a bad alternator. There can be a short in the alternator that seems to be easy to overlook. It has happened to me so many times that I just start by replacing the alternator with one known to be good. It may charge fine, but be the source of a current draw with the ignition off.

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  • studevic
    replied
    thank you for your help , tomorrow i will start tracing the field wire , cheers from roger

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  • rstrasser
    replied
    studevic;
    The field wire should only be energized when the ignition key is in the run position. The field receives its voltage from and is controlled by the voltage regulator. The regulator controls the amount of voltage being applied to the field coil to regulator the output of the alternator.
    You said that it overcharges when the field wire is disconnected from the regulator but stops charging when the field is disconnected from the alternator.
    Time to start tracing the wire connected to the alternator field terminal.
    Ron

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  • altair
    replied
    I had a similar thing happen and by elimination it was the starter motor. It was extremely dusty inside and causing a drain to ground. Try pulling the cable off the starter.

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  • studevic
    replied
    ok , i have just disconnected the field wire from the alternator and the drain stopped , i tested the supposed field wire and it has power at all times , is this normal for the field wire , i think some of the wiring is stuffed up if this is the case ,thanks from roger

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  • TWChamp
    replied
    Try unplugging the alternator to see if the drain stops.
    Also check for a trunk light being on.
    Since you mentioned the wiring was messed with, you may have to just keep pulling fuses or disconnecting anything that might draw about 2.6 amps.

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  • studevic
    replied
    hello all , i have just used the amp meter as in post 2 and get a 2.6 amp reading , i have also pulled the fuses one by one , nothing changes , what gets me is that it still overcharges with the field wire disconnected from the regulator , i wonder if the wiring to the alternater is not hooked up right as some wiring was messed with by the previous owner , anyway i will let you know if i find the problem ,thanks from roger

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  • TWChamp
    replied
    You should do as I mentioned in #2 and use an amp meter to get a reading of the actual amps being drained. This might help to locate the source of the problem. On an unknown measurement, always start with the highest meter setting and work down to the most usable scale. Many multimeters won't read more than 10 or 20 amps, so if you got a heavy spark at the battery post be prepared to use a larger meter or put a headlamp in series to drop the current, while you check for the problem.

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  • Skip Lackie
    replied
    Suggest pulling one fuse at time as a way to ID where the short is. The spark will not appear after you've pulled the fuse on the bad circuit.

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  • studevic
    replied
    hello all , thanks for your advice , i have tried two different new batteries same thing happens , i followed doofus advice and yes there is a short somewhere as the cable sparks when touching the battery ,i will keep looking ,cheers from roger

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  • karterfred88
    replied
    Either there is a large current draining short, or the battery is bad. You can shove electricity into a battery that won't hold it. Test for the short like doofus mentioned, if not there, take the battery out and exchange it with one in another vehicle that operates correctly. Internally shorted batteries can test fine for 12 volts, even have the proper hygrometer reading for the acid and be dead ducks.

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  • altair
    replied
    I would say that there is nothing wrong with your electrical system your alternator plus components are doing what they are suppose to do. Your trouble is clearly with your battery, replace it. Your battery is probably shorting with-in. If a battery is failing it is usually because of old age, if your battery is over 5 years old or has had limited use, failure is imminent. When a battery starts to fail it is like trying to keep a bucket full with a hole in it, you can keep the tap wide open (alternator over charging) it is not over charging the battery it is just trying to keep up) and you can not fill the bucket. If you fix the hole in the bucket then you can turn the tap off.

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  • Mike Van Veghten
    replied
    In any case, the alternator is not over charging. The alternator will charge to its maximum depending on rpm, at all times.

    Its the regulators job of..."regulating" that charge amount.

    Mike

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  • doofus
    replied
    Easier yet, pull + batt cable, with everything turned off shade batt. and try to see if you can get a small spark when touching cable to batt. happened on wifes 57, bad wiper switch. Luck Doofus

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