Replace wiring harness?

[magic930]

Just in the process of removing the wiring harness and noted that in a number of places the outer plastic is cracked, oil and dirt has slipped in and the whole thing is extremly stiff. The car is an 87 turbo so at 16 years and 113K miles is this part about to start giving me problems. Keeping in mind that it's not a cheap part!!! Is it typical to just replace it during a rebuild before it exhibits problems?

[Jim Sims]

Well, an inexpensive option is to clean the whole harness up, make cuts through the wires where the insulation is brittle, slide on shrink tubing, solder the wires back together, then shrink down the tubing. Shrink tubing can also be used to reinsulate the "Faston" type connectors. Right angle spark plug rubber boots can be used to replace the boots on the larger connectors (such as on the back on the alternator). I did this on my '76 as a temporary measure; next time the engine is out I'll probably replace the engine wiring harnesses.

That being said, a significant issue with the dependability of older engines is faults in the wiring. On my son's '73, the wiring was so bad that we just elected to buy new harness sections (all the way to the CDI box and the 14-pin connector) for the engine. The OEM replacements from Porsche duplicated the old harness down to the smallest detail. Costly though.

Also consider replacing the rubber/fabric portions of the fuel and vacuum lines given their ages.

Cheers, Jim

[oneblueyedog]

I had the same problems with my harness too. All of the wires exposed outside the tape were work hardened. I went a little crazy in restoring it though. And it didn't turn out stock looking. I had previoius experience with a 914 harness (wich has a control unit for FI). I learned that you use a heat gun (model RC plane type on hand) to heat the wires to make the insulation flexible enough to bend. I figured this out because I had to move some wires around while the engine was hot. After the engine cooled down, I had to move these same wires-and they were hard.

On the SC:
I removed all of the old taping.
I made a special tool to take the terminals out of the plugs. It was a flattend common nail ground to a tapered point that would bend in the tangs that keep the terminal in the plug.
I made diagrams of the plugs and the terminal ports and the terminals that went in them. I then cross checked that with the manual wiring diagram.
I removed the terminals from the plugs.
I removed the rubber tubes and grommets,heating the harness as I went as to not fracture the insulation of the wires.
I temporarily wire tied the wires that ran out of the harness to the components.
I then went on a search for boots.
I used alligator clip boots for the Bosch FI terminals that were rotten. I made sure they could stand heat. I found the ones that did. (True Value Hardware). Use the black ones. The 90° bent rubber boots were repalced with rubber boots I found for lawnmower spark plug terminals. I got them for the alternator.

For the rotten wires, I solder spliced them this way:
Start with the untaped harness.
Get the end that is rotten and trace the wire deep into the main harness.
Discover that the wire is actually a differnet color from the end because of all of the heat cycling.
Measure all of the hardend wire on the end. Get as much as you can. Remove the hardend stuff.
Take some new wire the same gauge as the hardend wire and measure it out to the same length as what you cut off.
Make a cut in the wiring harness that is same wire you took the hardened wire from. Cut it in far enough in the main loom to hide the "new length" you cut to replace the old hardend wire.
Take the end of the cut (coded) wire that travels out to what you cut off and take that end and re-route it out to become the new teminal end. You are making the wire do a 180° flip.
Now you solder the splice between the flipped end and the cut in the center of the loom. Be sure to heat shirnk cover the soldered splices. This gives you a correct color coded wire at the end. It's totally necessary for maintenace in the furture by a mechanic or next owner. The splice is deep in the loom, hidden away after recovering it.
If you salvaged the old terminal end, solder it on. You can buy new Bosch FI terminals at foreign parts stores to replace the broken ones.
I soldered new terminals on where I had to.
I covered the harness with heat shrink tubing(a la 914 but black) of various guages. It was a real bear. You have to cover it in pieces. The strategy is to telescope the tubes over each other a bit, especially where a wire runs out of the main harness.
Brittle wires won't take this process. I was lucky enough to find a vendor that had heat shrink uncut on rolls. I re-did much of it on account of trial and error. They were selling the stuff at 49¢ a foot (1" +or more in diameter)so I could do some experimentation. I know why Porsche taped them. A really hard job, but it came out great. No bare wires.
When you re-install the terminal ends back into the terminal plugs you have to carefully bend the tangs back out to get them to lock into the plug.
I tested continuity for every wire and all had curent flow. Success!
Make sure your heat shrink can withstand open flame without igniting. The boots won't take flame, but the old ones didn't either (rubber).

This process may be useful for a totally shot harness that can't be replaced.

Oneblueyedog

[magic930]

Thanks for the suggestions not sure which route I'll take yet, will probably wait to see what other parts I will need inside the engine first.

[PJMARKOW]

Speaking of the engine harness, has anyone built a new harness using the old one as a guide. After having programable EFI installed on my 1977 930, there are a few redundant connectors in my engine harness and I was thinking of building a new one, using the old one as a guide.

[magic930]

Rebuilding mine with new wire has crossed my mind, I wish I could easily find a new set of plugs and speciallty connectors, I have found that buying unique eletrical connectors is difficult. Most manufacturers want you to buy in huge quantities because the connectors are so cheap. Finding exact matches is difficult. I wonder which company makes the current "vintage" Porsche wiring harnesses? maybe they would supply a kit of connectors.

[oneblueyedog]

The Bosch FI connectors are expensive. $12.00 is what I paid for them. They were correct though. The connectors on the CD box (78SC) are blade connectors but they have that little locking tab to hold them in the plug housing.
I think it would be really hard to find color coded wires that match Porshe and make a harness from scratch. There are some amazing people out there though.
Maybe try some concours/restorers BB's.