Pertronix-unfused (1863)
 

Installing a new "ignitor" in my 72. The directions show the red wire being hooked up to the +side of the coil. Seems to me.... It would be better or safer to go into one of the three fuses on the control panel and tie it to the fused side thus protecting the unit???? Not sure which one to hook it up to, but that is my theory???

My advice, don't second guess the manufacturer. The Petronix is designed for a direct current from the coil as are mechanical points, adding a fuse is asking for a weak link in the ignition "chain" to break--while driving, no less.

for what its worth, here is a thread i started a few months ago about my Pertronix install in my '73 911e.

http://forums.pelicanparts.com/porsche-911-technical-forum/412669-pertronix-installation-73-911e-complete-photos.html

i don't know if it answers your question about "why", but my install came out swimmingly.

UPDATE: PERTRONIX DOES NOT HOOK UP AS PER STANDARD PRINTED INSTRUCTION ON A PORSCHE WITH A CDI UNIT. DO NOT HOOK IT UP A SHOWN ON THEIR PRINTED INSTRUCTION SHEET. e.g. "connect the IGNITOR black wire to (-) side of the ignition coil, connect the red wire to the positive (+) side of ignition coil. THIS IS NOT GOING TO WORK. IN MY CASE, THE BLACK CONNECTED TO THE EXISTING EXTERNAL (1-BLACK,1-BLK/PURPLE) WIRES CONNECTED TO THE DISTRIBUTOR. THE RED I EXTENDED TO A IGNITION SWITCHED LEAD @ THE 3-FUSED CONTROL UNIT. OTHER THAN CALLING AND ASKING THEM, THE ONLY PLACE YOU CAN FIND FURTHER INSTRUCTION (A DIAGRAM) IS IN THEIR TROUBLESHOOTING SECTION.
NOTE: FUSE IS NOT CALLED FOR BY MANUFACTURE (SEE OSSI-B)
YOU CAN SLICE INTO THE CDI UNIT (SEE RICK'S....73 INSTALL--NICE WORK)

here is the correct picture from the Pertronix website for a CDI install.http://forums.pelicanparts.com/uploa...1257909043.jpg

Agree... do not wire the Pertronix to the coil with a CDI.