Electrical: alternator overcharging

[studevic]

hello all , can you please give me a few ideas on a problem i have with a 1965 cruiser , the amp gauge pegs out max when running , battery goes flat overnight also , i replaced regulator ,same thing , alternator replaced ,same problem , so i disconnected a wire at the regulator and when running the amp gauge still shows max charge , the wiring on this car had been altered in the engine bay before i bought it . any help would be welcome thanks from roger

[TWChamp]

Remove a battery cable and put an ammeter in line to see how many amps is being drawn off by a short, or something being turned on. It sounds like something is killing the battery and then the alternator is running full charge to recharge the battery.

BTW, draining a lead/acid battery is very hard on the battery, and I read years ago that each time the battery is drained it has just lost 10% of it's life for good.

[doofus]

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

[Mike Van Veghten]

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

[altair]

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.

[karterfred88]

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.

[studevic]

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

[Skip Lackie]

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.

[TWChamp]

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.

[studevic]

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

[TWChamp]

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.

[studevic]

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

[altair]

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.

[rstrasser]

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

[studevic]

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