1911 SC Charging Problem
 

1981 Porsche 911 SC with an alternator that has the integrated regulator.



The original alternator was overcharging 17 volts at idle. It then stopped charging and the red warning light was coming on. I checked the voltage at the battery and could only get 12 volts at idle.



I replaced it, with a rebuilt alternator. From the beginning the car idled lower and I checked the voltage at idle 12.9 volts. The car did drive fine except for lower idle, two weeks later the cars idle lowered even more and I could not drive the car out of the garage. Checked the voltage at the battery, no charging again reading 12 volts.



I removed the alternator again and had it bench tested. The company says the alternator is working fine. Installed it again, and no charging. One thing I did notice is the alternator light isn’t coming on as it did before.



Any expertise is appreciated

Check the alternator light. If it doesn't come on when you turn the key, your alternator will never charge. Tons of recent threads in the archives on this.

I think the alternator-warning-light-as-part-of-the-charging-system phenomenon was specific to some of the early cars. Not sure though.

At least through 88 and I'll check the 964.

Post your location! there might be someone in the area that would be willing to help you.

don't know if this applies to internal reg. but,

Battery terminal corrosion or old ignition switches have internal contact resistance often causing a lite "glow"........Ron

I was absolutely certain that some idiot was going to say that the 1911 SC didn't have an alternator. Or a generator for that matter.

Sure am glad some idiot didn't say that.

The alt. light MUST come "on" with the key in the "run" position,
or the alt. will NOT "start".

Good luck will your internal regulator alt. They're all less reliable
than the external ones. I'd convert my '88 3.2 to an external, if
it weren't such a hassle.

Have Fun
Loren
'88 3.2

Checked Light
 

Thanks everyone for the replies.

I checked the Alt. light. The light is on when I turn the key to on position.

When the car is running the light doesn't come on.

My Loction is Irvine California.

If your idle is to low the alternator will notoutput the correct charge. adjust your idle to spec and then check the output voltage.

Did you clean all grounds? At the battery, at the engine to chassis? They must be immaculate.

Did you bench test the battery? The battery takes a bit of a beating when it is overcharged by a flaky alt.

Of course the battery terminals must also be cleaned as well.

John