Wiring. This is one part of the project I put off for the longest time because well, it just ain't no fun. On cars this old and simple, it's not a difficult task-I mean, it's not like I had to worry about HVAC, or airbags, or ABS, or power locks, or windows, or...well, you get the idea-still, once even a simple wiring harness is out of the car it all looks like so much spaghetti. When I had removed everything from the car originally, I had made careful notes as to what wire went where on what component-BUT-some of the notes got lost, plus I had plans to modify a few circuits and add a few, as well. The modifications I wanted to make were:
- Replace the weak DC generator with a high-output alternator-which involves adapting all the voltage regulator and associated wiring.
- Replace the fuse box with a new ATO type.
- Install high-current power supply relays for new H4 headlamps-one relay each for low beam and high beam, but use the original low/high beam select relay (up in front of the pedal cluster) to activate them, but relieve it and the headlight switch from carrying all the active current.
- Swap the old horn relay for a newer, more capable and safer design.
- Add an electric fuel pump supply circuit, wired through the ignition switch and a disguised power switch.
- Add an LED 3rd brake light over the rear window, in the roof vent area.
- Add a battery cut-off switch.
- Add a power circuit for an MSD 6 AL ignition.
When working on any car's electrical system, you need a diagram to show how it's supposed to be wired, so you can figure out if it really is that way, or not. My 912 shop manual had a small, black&white wiring diagram, but it was hard to read while working on the car, plus it being B&W, it didn't show what the wire colors were. Luckily, 911's and 912's use the exact same harness-it's just that a few connections the 911 uses don't do anything in the 912-(the oil level sender harness, for instance-912's don't have an external oil tank like the 911's do-they're wet-sump engines). There were quite a few bundles of wires here and there not hooked up to anything in my car-no foglights(white wire w/green stripe in the horn harness), no hazard flashers (extra bundle near the low/high beam relay up in front of the pedals), no clock, etc-I wanted to be sure what they were supposed to go to to make sure some previous owner hadn't disconnected stuff and just left the wires dangling or hacked the wiring for some funky accessory no longer present. Pelican Parts has large, full-color 911 wiring diagrams for almost any year on thier website- here's a link to the one I used. Downloading the 1965 911 diagram and printing it out in a large size made working on my harness MUCH easier-I just had to keep my 912 diagram handy for the few things that were different. Of course, after I had done all the work, I came across a great, full color 912 diagram on a fellow 912 owner's site -wish I had found that a few weeks sooner! Once all the repairs and modifications are done, I'll re-route the harness and protect it with convolouted flex tubing.
About the fuse box…mid ‘60’s Porsches use the same type of fuses as VW’s of that era-those funky little tapered, metal-covered plastic tubes. The original fuse box in my 912 was a sad sight-corroded terminals, bent fuse tabs, and a rat’s nest of wires. Since I was planning to drive the car to out-of-town races and rallies, I wanted to upgrade the fuses with something a little more common (and more reliable). I considered swapping in a new-style ATO (blade–type) fuse box out of a junkyard car, but didn’t really want to take chances with a used electrical part. Painless Wiring and a few others offer fuse panels that include everything needed to wire a car from scratch-the panel itself, fuses, circuit breakers, flasher units, the whole enchilada-but I didn’t really need all that, as I’d already installed relays for the high-current devices-and all I really needed was just a fuse box. I finally ended up using 3 4-fuse units from Ron Francis Wire Works to duplicate the wiring of the 12 circuit original fuse box, which will make future troubleshooting and repair easier. The new units have removable terminals and are modular, which allowed me to move wires over from the old box a little at a time, instead of all at once-then slide the units together once all the wiring was completed. I cut off ¼” of each old wire, crimped and soldered them into the new terminals, insulated the connection with shrink tubing, then inserted them into the new fuse box. The whole job only took a few hours, less than $20, and now offers better reliability, easier parts availability, and peace of mind.
