Electric fire 1977 911s Targa Help Request

[mxrider1979]

Hello all,
I figure for my first post, I should make it a really difficult one! The following images are going to be of the mess I have made so far.
This first one, burnt wire in the front of car:


Next is rear of car:


This image is where I am stuck: Going toward the rear of car, how do I get to this wire bundle?


I have every manual there is for this car, but it is not helping me out too much as I have lost track of where the wires physically run. Also, I have searched these forums literally for about 3 hours; the closest posts I could find were:
Dash lighting fuse installation
and
Is this circuit a fire hazard?
I am still stuck, any advise on a next step would be great. In the meantime, I plan to study the current flow diagrams.
Thanks much all

[Joe Bob]

You may be best served by getting a new/salvaged wiring harness. What fuse served the burned wire? That blue jumper cable looks to be a problem as well.

[kach22i]

I'm stumped.

Would photos of existing 1977 wiring details help you?

[mxrider1979]

I believe it is fuse number 8, but to be honest, I don't really know as I don't have the stock cover.

I picked this car up from a cousin as a gift. I figure I would spend my vacation time to get it running, but the cold is really slowing me down!

Let me know if more pictures would help as there is a lot going on with this car. It has an 84 Carrera motor in it as well; not sure getting a wire harness will help all that much.

From what I see with this harness, there are so many places where the wires branch off. It looks like it would be a major ordeal to change it out. I was really hoping to isolate the burnt wires and avoid stripping down the entire car. Also, I'll have to figure out where the short started.

Thanks again

[mxrider1979]

kach, yes that would probably help out. I did take pictures of everything before I started to pull it apart, so I might be ok there. I think the biggest issue is going to finding what is burnt up and what can be salvaged.

[schumicat]

have you taken off the access panel under carpet in the rear seat area (held on by 4 screws)? I think the wires bundle may run through there.

[mxrider1979]

I was just about to start that today, I needed to grab a short handle phillips screwdriver. Unfortunately, I don't have my own garage so I am lugging tools from my parents place over to my grandparents home.

My guess is I will find more wiring here, but most of the wire bundles run along the floor. Also, I am trying not to destroy the interior, there is a lot of adhesive hold things together. I wasn't sure if that was common for that year. The floor mats all along the bottom and sides of the car were glued in place.

[frankc]

Where did they place the DME box when they did the 3.2 motor swap? Normally, I believe, it would be under the right seat. This might explain some of the wiring mess since the '77 CIS motor did not have any type of computer so they would need to run a new harness to wherever they put the DME box.

btw, I also have a '77 Targa if you need any wiring pictures, although most of my engine wiring is gone due to carbs.

[mxrider1979]

frankc, you're right, the box did get placed under the drivers seat:

They ran these wires low along the drivers side and drilled a hole through the engine fire wall. There is a giant mess of black silicone holding it in place, fortunately nothing here looks burned up. After looking at the current flow diagram, I am thinking I am in for a lot of work as a lot of wires just don't match up.

[boyt911sc]

mxrider1979,

Could you take some pictures of the engine bay left side area where the 14-pin connector could be found? This is the connector that connects the engine wire harness to the chassis wire harness. Start analyzing the wires at the 14-pin connector. One direction towards the engine (which should be easy) and towards the chassis.

You could only do a meaningful investigation if you know and understand the wiring schematics for the chassis and engine (Carrera 3.2). Keep us posted.

Tony

[RoninLB]

if me i'd go right after the cause of the shorted wire and forget about the rest of the harness



fuse #8 from the front of the car is listed as "high beam left" on the 1977 fuse panel cover

"high beam left" has a solid blue wire going directly to the left headlight bulb

the Workshop Manual wiring diagram shows L1 bulb, blue wire, then S8 fuse

also L1, green/yellow wire, then S6 fuse for panel named "low beam left"


there is a chance that the headlight wiring received a two or four relay up-grade that removed the main high current being drawn by the headlights from your cabin turn signal and headlight switch.
ie: the headlight switch and turn sig switch are only used to trigger the relays with a low current

i'm not sure i'm headed in the right direction with your car at the moment but right now if i am then you might have the left headlight wire connector melted and grounding out the wires




also set up a signature with all up-grades to your car to make it easier for members answering your next issue

[Flat6pac]

The 14 prong connector in the rear is engine information.
The harness through the tunnel goes through a small corner channel in the tunnel.
What I have done in the past is stagger cut the harness through the area forward of the pedal cluster after having brought the cut harness from the rear to the front through the tunnel.
The 3.2 install requires coil power from a fuse that is hot and stays hot through the starter on/engine start. The 3.2 harness is a completely separate harness that belongs under the drivers seat as installed.
I m trying to figure if the harness through the tunnel is burned. If it is the wire probably burned the wires next to it also.
The blessing is the schematics for the 77 are in color in the manuals.
Bruce

[mxrider1979]

Tony, here are a couple more shots of the engine bay wiring, they are all a little too zoomed in.





I will get new ones today a little further back to show where they lead. They more or less go straight back toward the cabin, then oddly enough, they make a right turn toward the passenger side of the car and that is about as far as I have traced it, the motor doesn't leave much room to get my hands in there.

I will start taking down the air filter housing and other stuff that is in the way today along with everything else in the back seats. I saw on another thread that a heat gun will be handy as it seems everything really is glued down on the inside.

Ronin, I'll pull the headlight switch and head lamps out as well to see if anything there has fried. I'll also work on the signature tonight when I get home, no computer at grandma's.

Bruce, the tunnel wires appear to be the wires with the most damage. One wire did burn completely through its insulation and fused about 7 other wires together. This tunnel wire is where I have the most trouble as there is no slack going toward the engine. I figure since it cooked, it made the wire very stiff, so that is the part I have been stuck on. Looking at the first post, that is the 3rd picture. I cut those wire inside the trunk and pulled them down past the pedals to that point. That alone took a lot of muscle since everything is so rigid.

Can't thank you guys enough for the help so far. I have a good straight 6 or so hours to work on it today, I'll check back in later to see if any new ideas popped up.

[RoninLB]

Originally Posted by mxrider1979

Ronin, I'll pull the headlight switch and head lamps out as well to see if anything there has fried. I'll also work on the signature tonight when I get home, no computer at grandma's.

don't pull the headlight switch yet

your pic shows a fried blue wire?

if so start at the fuse box and see where that blue wire goes

[mxrider1979]

Ronin, sorry no that is not a blue wire, it looks blue though after the insulation melted completely off.

I made major progress today, pulled the chassis wire harness out from the fuse box, through the tunnel, and out the engine fire wall. The fried red wire I believe is the culprit. Looking at the current flow diagram, it is either the ignition transformer, fuel pump, or fuel pump relay. There are so many wires, I'll have to take a better look to make sure I did read that right. I still don't know what caused the short, but at least I know what needs replacement. There is just a lot of melted wires, would stink to rewire and have another melt down!

More close ups of the burned wires:



A good chunk of fried wire:


If anyone has had a similar instance, feel free to let me know your steps to getting the car back to the street.

[boyt911sc]

mxrider1979,

Thanks for posting the pictures of the rear fuse panel in post #13. Although I could not clearly see the 14-pin connector I was looking for, it could be that piece seen in the second picture (upper section). That's a lot of wire to replace!!!!! I would consider using a good used wire harness from the dismantlers. The time and effort you'll be utilizing to get the burnt wire harness back to workable state/condition is not economical or practical. It would take you days to refurbished this damaged harness back to life.

If you factor the time and aggravation in making the old wire harness usable, a $100 plus purchase could solve all these. BTW, I have a '77S roller with only 49K miles in my garage I'm working this winter. We could use it as guide to your wiring project. Keep us posted.

Tony

[mxrider1979]

Tony, I searched for a harness online, they are pricey! I also googled dismantlers, the big one seems to be LA dismantlers. I will have to give them a call as they don't have one listed online or on ebay. Maybe there is a local yard that might have one? Also think $100 bucks is the right price for a new one?

I was thinking to hit up Radio Shack after seeing this site:356 Porsche Technical Articles - Installing a wiring harness Part I

I know it is a different model, but same idea. The tunnel is tight so I was thinking to make a new hole either in the tunnel or right in the engine fire wall and run the next harness along the passenger side doorway. I fought to get that old one out, going in I can imagine will be just as painful, if not worse!

Thanks again Tony,
Will

[mxrider1979]

As everyone can tell at this point, this project is consuming my entire vacation. I'll have to thank everyone and curse everyone again for helping me out! Thanks for the terms like tunnel which lead me to this thread:
OOOOOPS, What's in the tunnel?
But curses for making me spend hours on these forums! Just kidding! I do appreciate every bit of help I get.

[mxrider1979]

Anyone selling a wire harness for a 77 911s?

I finally got the full harness out from front to back, there are some tight spaces!

One wire alone did indeed burn from trunk fuse box to engine fuse box. I am on the hunt and will be searching the dismantler sites as well as local junk yards to see if I can dig one up. I have found some used ones as well online, but still in the upper $300 range. I did find a website that sells a 500ft spool of auto wire for $32 bucks, I have plenty of masking tape, maybe i'll be a shut in next weekend and just make my own?

Thanks again all, and if anyone has an idea on what might have caused the short...

Happy New Year all!

[lucittm]

Will,
There are 1000 reasons as to what caused the wire to have become shorted. That is not your problem now. This is a doable project but you will have to become obsessive about organizing and systematically attacking each circuit one at a time. The Porsche engineers were pretty straightforward in their thinking, but there are some anomalies you need to be aware of.
1. Make sure you use the correct gauge wire for each circuit, these range from .5mm to 6mm (find the conversion to American Wire Gauge online).
2. Learn the basic color coding, such as brown for grounds, red for +12v power, grey for tail lamps, etc.
3. Get a good meter and check all your connections.
4. Buy a good crimper, the heavier the weight the better quality it will be.
5. Purchase a large quantity of 10-12, 16-18, and 18-22 gauge "splice-in" crimp connectors. The heatshrink waterproof are the best, but they are pricey.
6. Make a list of every connection "from" and "to" on a spreadsheet from the wiring diagrams that show circuits from the front to the rear. You will see patterns develop and as you replace or repair each wire, cross it off the list.

I had a 1977 911S, it was the BEST car I ever had. You will be rewarded with all your hard work. Just make sure you have the ownership papers in your hands because your cousin will want it back when you get finished with it.

Good Luck and keep us informed. There are many 911S 's out there and the owners are anxious to help a guy like you willing to invest the time to bring one of the old girls back to life.

BTW, there are many circuits that are connected to the battery and therefore they are always "hot". Any one of them could have been shorted to ground, don't install a battery until you can verify that the positive battery post is not grounded.

Mark