Porsche Repair: Generatorlight, voltage regulator, voltmeter

Question
Dear sir,

In the past I've asked you some question, on wich I always got satisfying answer, so here's another question. I own a 1964, 356 SC. My engine has just been rebuilt. When yesterday I had it running for the first time since one year, it started up good. But, on the dashboard the left red light (for the generator) keeps on burning and doesn't go out. We don't understand what could be the problem. Do you have any idea? I hope you can help me.

With kind regards,

Erik Vink
The Netherlands.  

Answer
Hi Erik, nice to hear from you again.  And now you have a freshly rebuilt engine too!  You are very fortunate indeed.  Let's get to the bottom of your tell-tale light quandary:


The light could be malfunctioning or the generator may not be charging suffciently.  Let's see.

1.  We'll test at the voltage regulator.  Turn the ignition on, but don't start the car.  Verify that your tell-tale light is indeed on.  Then disconnect the wire at terminal 61D+ of the voltage regulator, and the light should go out.  If not the light is malfunctionaing because that wire is grounded by mistake.  If the light goes out as expected, reconnect the wire to the terminal it came from..

2.  Next, with the ignition off, disconnec the wire at terminal 51B+ and move it so it cannot be grounded by accident.  Attach your voltmeter probes to terminal 61D+ and to the regulator base, which should be grounded.  Start the engine and run it over idle until your voltage reading exceeds 6 volts.  Of course, if there is no reading the generator is not charging.

Let's stop at this point and I'll await your comments as to test results.

I hope to hear from you shortly.

Dave