911 Wiring Harness

[thebigiguana]

I have a '77 Carrera Euro (3.0) and the wiring is an the brink
of a diaster. I have retro fitted some wiring to relieve the known problems, but I'm not a big fan of quick patches for the long term. I know the is a common problem, and am willing to do the right things make it right.

I would really like to get a complete wiring harness and make the car whole. I was once told in passing this can only be ordered from the plant and they make it per the VIN and engine number, taking 6 months or so. Is this true ? If so, do you go through Porsche or LEONI (the sub for the electrical)? Any ideas on a contact person/place?

Or am I just better off running new wires as I can ?

Any help or suggestions are appreciated.

Thanks !

John

[atr911]

I had very similar problems with my '78. I did some research and found that the OEM replacement from porsche (there was an original part number on the main wiring harness) was exceptionally expensive.

It took me some time, but i was able to track one down (sorry i can't remember from where) I think i paied about $150 and when i got the part I was pleasently supprised at how well all the wires matched up.

On a side note, I also opend up another harness that wasn't quite as FUBAR'd and was able to easily repalce the few wires that were melted.

Hope that helps some!

The long lost,
Adam

[Ove]

John,

I have encountered a lot of electrical problems on my car, mostly with the lights.
My advise would be to look at the fuse box first. There may be other problem elsewere in the electrical system, but I have traced almost every sigle problem I've had down to the fusebox. Corrotion is the key word here.

This is what I've done:
- Replaced all the fuses
- Used sand paper on the fuse connection points in the fusebox
- Inspected the wire ends where they meet the fuses. Some of them were green from corrotion, so I cut the wires a bit, then soldered the ends.
- Removed, sanded and put back the wires that looked corrotion free, tightening the screws well.
- New wires directly from the battery to the low beams. Fused of course, and via a relay for each of them. The original wires now just triggers the relays. Will do the same with the high beam wires.
- New wires and new style fuse for the fuel pump.

To permanently solve the fuse box problem I have just made a new aluminium fusebox. This accepts new style fuses, and also more fuses and relays than the old one did. I will still be using the round relays to retain the original look. Not quite finished yet, but I can post some pictures after the weekend.

The wires themselves are rarely a problem in my experience, although they may corrode in each end where the wire core is exposed/connected. However they may melt if they are not fused or if the fuse fails. Other german cars from the same period probably use wires with the same color coding if you are looking for a correct colored wire to replace a melted one.

Hope this helps

[thebigiguana]

This info is perfect ! I'll start with through cleaning what I have on the present fuse panel and connectors. I'm way ahead of you on the new line for the fuel pump. That was a "must-do" on a road trip.

I'll keep my eyes opened for a wiring harness to patch in the bad parts. You've given me hope that there are still some good harnesses out there. If you happen to see/hear of one or a place to snag one, please let me know.

Just for the record, before I got my 911, I was told by other Porsche owners, that "you will find that there is no greater group of people nor individuals willing to share and help you in any way possible". While I have owned my 911 for less than a year, I can attest that this statment is very true. Good people, good cars.

Thanks !

- John

[Jim Sims]

One can also replace sections of the wiring harness; such as those on the engine and in the engine compartment that age more quickly from the heat therein. These new sections are available from Porsche (at least they were a year and half ago), are relatively expensive but not nearly so dear as doing the whole car. They are correct and OEM though down to the smallest detail. I have replaced the engine wiring harness sections on a '73.5 T CIS using these Porsche OEM sections. Cheers, Jim

[Ove]

Thanks for your kind words, John,
Doing the wire harness/electricals is one of my winter projects. I have a few non factory wires on my car too, and will be replacing them. A friend of mine has a '85 BMW 528i wreck from which I thought I could get some wires. I'll go and have a look at it next week to see what I can use. It's not the end of the world if they are not an exact match, but I hope they are close.

Which wires do you need?
They will be the same color on my car, so it will be easy for me to compare.

[silverc4s]

If you still want to purchase a USED wiring harness, or a part of one, try Partsheaven, in Hayward, CA. They advertise in all the P car mags, great guys to work with. My motto - NEW PARTS, WAYNE, USED PARTS, Partsheaven...

[Bobboloo]

To add to the previous post. Aside from the fuse block all the connectors in the harness should be cleaned as well. The wires really don't go bad unless they've had an improper amount of current going through them.

Some wires might get a little hard and crack if they are exposed to too much heat. (laying on a heat exchanger??) But that shouldn't be the case unless the engine tin is missing.

An easyfix is to buy Tuner cleaner at Radio Shack (if they still sell it). You just pull the connector off, spray the connections, and plug and unplug a couple of times. If Radio Shack doesn't have it go to an electronics supply and ask for contact cleaner. Do this for your motor for the 14-pin connectors and the CDI box connector as well as any other connector and your motor will love you for it.

Bobby

[Jim Sims]

Au contraire! 911 engine wiring does fail and it doesn't have to even be up against a hot exhaust part. On my '76, some of the upper engine wiring going to several of the CIS components had experienced both the insulation becoming brittle and cracking but also the copper wire had broken. The failures were most evident where it appeared the wire had been flexing over the years. Also, the rubber insulating boots on the portion of the harness attached to the alternator were crumbling along with the grommet protecting the wiring harness as it passed through the shroud. Repairs were effected with a soldering iron, plastic shrink tubing and trimmed right angle spark plug boots and a generic rubber grommet procured from NAPA. These repairs along with some air hose replacements cured the cold start problems. Next time the engine comes out it will get new OEM engine wiring harness sections. IMO, one the best things one can do to make an older 911 engine reliable is to replace the engine wiring harness sections (followed by replacing rubber elements of the fuel and induction systems). 30 years of heat, vibration, hot oil and being out in the weather take their toll. Cheers, Jim

[thebigiguana]

I have to thank everyone that commented. This is a great way to get much need advice and insights.

Ove - Thanks for the offer. I'm going to see if I can find some items locally before I put you to any heartache.

I'm also going to follow up with Partsheaven and see if they have a decent harness.

Oddly enoughly, the wires that have given me problems to date have not be around the engine. It's been the very ones that have been protected for the most part (like in the smugglers box). Thus, I was concerned about the *overall* nature of the wiring.

It seems to me that the general idea here is that the wiring needs to be monitored, cleaned as possible, and the critical runs replaced as soon as possible, but that as a whole, the harness should be viable. Is this a fair generalization ?

If you have more suggestions or ideas, please, let me know. I am very eager to learn and open to any insights you may wish to share.

Thanks to all

- John