Hey Guys, I'm working on my sons 82 V8 S10 and the battery seems to be over charging.

I assumed it was the alternator and replaced it but still having the problem.
It's a new alternator and has the built in regulator shows 14 volts when running. Any ideas on what is going on? :confused:

Electrical problems are not one of my strong points.
Thanks in advance for any help I can get. :beers:
Jim

Measure voltage at the battery posts, should be within 0.4 volts of BAT terminal on the alternator. Use a Multimeter and do not rely on the dash gauge.

If voltage at battery posts is a match to alt, then battery would be at fault. How old is it? More than 5 yrs pld, might consider getting another one.
Do you have another battery to swap out and do the same experiment?

You can also test the battery with a battery charger and a voltage meter, if the battery voltage goes over 15.5 volts with a 40 amp boost then the battery is shot.

Dan E.
69 SS396 4spd. 4.10 posi. x66coupe

The only real way to check a battery is with a carbon pile....or a cheap hydrometer...looking for any calles different from the rest.

Seems to be overcharging? Is it or isn't it. 14 volts running is not overcharging. 15 volts or over I would start looking. Assuming new alt is good, overcharge can be caused by a bad ground, a bad battery, a battery that is low on acid, a bad sense wire, or a battery that is already overcharged. If the bat was over charged and maintains high voltage the regulator in the alt CAN'T lower the voltage. The reg can regulate voltage as it rises only. As volts rise the reg can sense and control further climb, but if voltage is already over the regs set point it will have no control. If there is a surface charge on the bat (high volts) from a previous over charge condition it will need to be lowered before running the new alt. This can be done by leaving the head lites on for a few min, or cranking engine till volts drop to 13. If the old alt was overcharging check bat acid level. If you have 14 volts running I would leave it alone. Mark

If I'm not mistaken, that alternator is a CS style and has remote voltage sensing. I wouldn't be surprised if the connection between the remote sensing lead (red wire on the 5 position connector) and the charge wire connection to the system (big red wire) has developed a bad connection. Almost sounds like the alternator is trying to bring the system voltage up to the sense level and burning up the battery in the process.

In addition to measuring these voltages (looking for approximatly 14.5 volts) with the engine running...
* Alternator charge wire lug on the back of the alternator and the alternator case.
* Battery (+) and battery (-).

Also measure the voltage drops. Look for low voltage (less than 0.1 v give or take) while the engine is running.
* between battery (+) and alternator charge wire lug on the back of the alternator
* between battery (+) and a known system voltage test point (perhaps a fuse in the accessory fuse panel).
* between battery (-) and the alternator shell.

Those 5 measurements will isolate the root cause.

Mine did that a few years ago. Everything measuured good at idl to 1500 or so then when id go down the road she'd be up around 3k or so it would spike and blw headlights then boil over. Borught it up to 3k in the garage and it was at 17 volts. Put in a wells solid state regulator and all is good.