Well, I decided to put everything I could find about early car engine electrical systems into a single thread. I'm going to be replacing my battery soon, and will be replacing various tired components with exact original replacements-- so thought I would do some research first.
It all begins with the wiring diagram. SWB cars have several features that set them apart. There is no BHKZ unit (All right, everybody calls it the CDI box. But Bosch-Hochspannung-Kondensator-Zündung just rolls off the tongue, no?). Secondly, they use a ballast resistor, which is always in the circuit between the ignition (on the same circuit as the fuel pump) and the coil, unless the starter is cranking, in which case it's bypassed and full battery voltage is delivered to the coil.
OK, so how does that translate into what's in the car? This is one of the hardest things for me to figure out-- the diagrams are good, but they aren't THAT good.
So it's off to whatever factory resources next. Here, the shop manual is helpful.
Image copyright Dr.-Ing h.c. F. Porsche KG. 1965
OK, now what color is everything supposed to be?
Well, for that we have to go to real-world examples. The best of which was the 37th 911 off the line, owned and lovingly restored by Alois and Estonia Ruf.
Lots of good detail here. We can clearly see the ballast resistor, with its plain black wires-- one to the coil +15 with the curls in it. Off the other tach terminal come the black to the points and the black/purple forward to the tachometer. Also, going into the bottom of the ballast resistor relay, we can see the red in the center, yellow on the right, black on the left and there must be a ground where we can't see it.
If you look in my car, which doesn't use the ballast, this is confirmed. (Pardon the oxidation!)
OK, so let's look at a few more from the Parade.
OK, do any of you SWB owners have photos of your own cars? It would be helpful in builidng a record. Also, if I've made any errors please let me know-- this is uncharted territory for me.
Mine (sad)
