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> Assistance with Restoring 73 Wiring Harness
doug_b_928
post Jan 31 2018, 03:55 PM
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My main Winter project is to 'restore' the wiring harness on my 73. I admit that of all the jobs involved in restoring this car, this is the one that creates the most anxiety in me. I took it out of it's container last winter, spread it out on the floor, and promptly proceeded to put it back in the container. But, the time has come to conquer this thing. I have 4 rolls of wire tape that cost more to ship to me than the tape itself, and I think everything I need to do the job. I have pieces of a 74 harness (which I'm aware is not the same) and have already used one of the correct connectors from it for one of the license plate light connectors. Overall, I think the harness could be a lot worse, but there are some areas where POs have made some modifications/fixes and I'm not sure what they've done and why. I'll be asking for assistance from the wiring gurus in the thread as I work my way through. I have the wiring diagram from Jeff Bowlsby's website, a multimeter, PowerProbe3, and cleaning supplies. I'm removing all the tape, inspecting, cleaning, and then installing new tape. I'm just going to clean and inspect the rubber covered sheaths as they seem to be tight around the wires and it seems unlikely that there is anything wrong underneath them (on the upside, everything that ever worked on the car during my ownership, which wasn't everything that was supposed to, still did right before I removed the harness).

Okay, so with that introduction, my first questions. Starting at the back, I've worked my way through the license plate wires, to the trunk light wires, and I'm currently looking at the fuel pump wires. My car had vapor lock, so the fuel pump was relocated to the front of the car. The mechanic just cut the wires, left the ground wire dangling, and spliced in a positive wire which he ran through the firewall (poking a hole; no grommet), under the carpet and through a hole in the front firewall, where he then spliced in the connector and grounded to a screw he added to the front firewall. Here's a pic of the wires:

Attached Image

Because of the vapor lock issue, I'm thinking I should put my new pump in the front where the old one was (by the steering rack). I'm thinking of getting the NAPA Bosch fuel pump (N69133). From what I can tell looking at the wiring diagram, and I could be reading it wrong, the power wire goes to the 'regulator/relay plate). If it's source was at the fuse box under the dash I'd splice into the wire up there and put the original connector back on the wires in the engine bay (in case I ever wanted to put an original style in its original spot. If I'm correct about the wiring diagram, then, with my limited knowledge, I guess I have to run the power wire on the outside of the sheath (but at least it will be inside the new 914 rubber snorkel) and up to the fuel pump in the front? Is there any point in running the ground wire that way too, or would you just ground it to a screw on the car as it was before?

Also, in the pic above there is a green wire that looks like it had a connector on it at one time. Does anyone know what that was for? When I look at the 73 diagram it only shows the black with red dots and the ground for the fuel pump. On the diagram it shows the, IIRC, 'fan blower motor' having a green wire. However, if that's referring to the blower motor for the heater, I think the wires and connector below were for that (note no green wire).

Attached Image

So, to summarize, what's the best approach for the fuel pump wiring, and what is that green wire for?
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dr914@autoatlanta.com
post Jan 31 2018, 05:11 PM
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cannot tell much from the pics but if it is a green wire with a black stripe and it is near the original fuel pump lead wires, it is for the optional oil temperature sensor. Original had a plastic housing around it and connected to another wire that was sheathed and led down to the bottom of the sump

QUOTE(doug_b_928 @ Jan 31 2018, 02:55 PM) *

My main Winter project is to 'restore' the wiring harness on my 73. I admit that of all the jobs involved in restoring this car, this is the one that creates the most anxiety in me. I took it out of it's container last winter, spread it out on the floor, and promptly proceeded to put it back in the container. But, the time has come to conquer this thing. I have 4 rolls of wire tape that cost more to ship to me than the tape itself, and I think everything I need to do the job. I have pieces of a 74 harness (which I'm aware is not the same) and have already used one of the correct connectors from it for one of the license plate light connectors. Overall, I think the harness could be a lot worse, but there are some areas where POs have made some modifications/fixes and I'm not sure what they've done and why. I'll be asking for assistance from the wiring gurus in the thread as I work my way through. I have the wiring diagram from Jeff Bowlsby's website, a multimeter, PowerProbe3, and cleaning supplies. I'm removing all the tape, inspecting, cleaning, and then installing new tape. I'm just going to clean and inspect the rubber covered sheaths as they seem to be tight around the wires and it seems unlikely that there is anything wrong underneath them (on the upside, everything that ever worked on the car during my ownership, which wasn't everything that was supposed to, still did right before I removed the harness).

Okay, so with that introduction, my first questions. Starting at the back, I've worked my way through the license plate wires, to the trunk light wires, and I'm currently looking at the fuel pump wires. My car had vapor lock, so the fuel pump was relocated to the front of the car. The mechanic just cut the wires, left the ground wire dangling, and spliced in a positive wire which he ran through the firewall (poking a hole; no grommet), under the carpet and through a hole in the front firewall, where he then spliced in the connector and grounded to a screw he added to the front firewall. Here's a pic of the wires:

Attached Image

Because of the vapor lock issue, I'm thinking I should put my new pump in the front where the old one was (by the steering rack). I'm thinking of getting the NAPA Bosch fuel pump (N69133). From what I can tell looking at the wiring diagram, and I could be reading it wrong, the power wire goes to the 'regulator/relay plate). If it's source was at the fuse box under the dash I'd splice into the wire up there and put the original connector back on the wires in the engine bay (in case I ever wanted to put an original style in its original spot. If I'm correct about the wiring diagram, then, with my limited knowledge, I guess I have to run the power wire on the outside of the sheath (but at least it will be inside the new 914 rubber snorkel) and up to the fuel pump in the front? Is there any point in running the ground wire that way too, or would you just ground it to a screw on the car as it was before?

Also, in the pic above there is a green wire that looks like it had a connector on it at one time. Does anyone know what that was for? When I look at the 73 diagram it only shows the black with red dots and the ground for the fuel pump. On the diagram it shows the, IIRC, 'fan blower motor' having a green wire. However, if that's referring to the blower motor for the heater, I think the wires and connector below were for that (note no green wire).

Attached Image

So, to summarize, what's the best approach for the fuel pump wiring, and what is that green wire for?
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simonjb
post Jan 31 2018, 05:45 PM
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As an aside, you can buy those connectors from Bughaus
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bbrock
post Jan 31 2018, 05:55 PM
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QUOTE(dr914@autoatlanta.com @ Jan 31 2018, 04:11 PM) *

cannot tell much from the pics but if it is a green wire with a black stripe and it is near the original fuel pump lead wires, it is for the optional oil temperature sensor. Original had a plastic housing around it and connected to another wire that was sheathed and led down to the bottom of the sump


(IMG:style_emoticons/default/agree.gif) I'm just a couple months ahead of you on restoring my '73 harness but mine needed a lot more work. I just need some sleeving and grommets before I can button it up with new terminals where needed.

For the fuel pump, mine had already been relocated to the steering rack area but it was a piss poor job and I'm going to move it up into the fuel tank compartment and add a late access cover. To do this, I bought a few meters of black/red 1.0mm txl wire off ebay (18 gauge is about the same gauge and gxl wire is a closer match to OEM) and ran it from the 14-pin connector through the sleeving up to the front trunk where the pump will go. I have a lot of sleeving missing, so it was easier than yours will be, but it can be done. Find a small stiff wire, make sure the end is blunt so it doesn't tear up any insulation, lube it with some glycerine or electricians lube, and fish it up through the sleeve. Then pull you new wire down through the sleeving. For the ground, I ran a brown wire salvaged from another harness from the new pump location up to the blower assembly under the cowl. When everything is buttoned up, I will add one of these: https://www.digikey.com/product-detail/en/t...627CT-ND/456719. You can't see it in that stupid picture, but it is a dual gender terminal with a male spade coming off the back. The plan is to plug this into the ground terminal at the blower, and plug the blower ground wire into the male spade. You could run your ground to anywhere you like, but this made for a pretty short wire run without having to splice into the harness. This way, the factory schematic will still be correct for my pump even though it is at the other end of the car.

If you need other spade terminals, you can get the OEM AMP terminals dirt cheap from digikey. I made the mistake of buying a bunch of no-name terminals on ebay before buying the good stuff from digikey.
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earossi
post Jan 31 2018, 06:15 PM
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There is a guy over on the Pelican Engine Rebuilding forum who has a cottage business going to fabricate new Porsche wiring harnesses. He's done tons of these and feedback on the forum is extremely good. Not very expensive either.
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JeffBowlsby
post Jan 31 2018, 06:20 PM
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When relocating the FP to the front note that the factory wiring gage changed significantly. Where the original location below the battery was 16 gage, use 12 gage if it goes to the front, per the factory schematics for 1975-76. For both power and ground circuits.
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mepstein
post Jan 31 2018, 06:21 PM
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QUOTE(earossi @ Jan 31 2018, 07:15 PM) *

There is a guy over on the Pelican Engine Rebuilding forum who has a cottage business going to fabricate new Porsche wiring harnesses. He's done tons of these and feedback on the forum is extremely good. Not very expensive either.

What’s his name?
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malcolm2
post Jan 31 2018, 06:27 PM
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Hope I am not too late. But I bought one of these wire diagrams for my 75. This one should be for you. Double check, cause he has FI, etc....

https://colorwiringdiagrams.com/products/po...e-914-1972-1973

Prospero's Garage
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doug_b_928
post Jan 31 2018, 06:49 PM
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Wow! Thank you to all of you for your helpful responses. The expertise on this forum just might get me through this (IMG:style_emoticons/default/smile.gif)

Thanks George and Brent for identifying that green wire. So, based on what George said I should put a new spade connector with plastic housing on that and call it good.

I have a pinning tool for removing connectors, but it's too short for these plastic housings. Will have to find something longer.

Brent, I think I'll have to study your posting for 2 weeks before I understand it (IMG:style_emoticons/default/smile.gif). It's great to know you've been through this. I can tell you are much more knowledgeable than me so you might have to dumb down your advice to beginner level so that it doesn't go over my head.

Great to know about the housings and connectors and Jeff's tip on wire gauge is awesome (I'd have tried to match it to what's there).

Thanks again guys! Unfortunately, there will be more questions coming but I'm feeling better about it already.
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gothspeed
post Jan 31 2018, 06:59 PM
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I am just about completed bringing my 73' harness up to snuff. There are tons of useful wire diagrams, sketches and pinout descriptions on Bowlsby's site (link below). I printed and referenced a great many of these. I am so grateful that Mr. Bowlsby keeps this information available to us! And if you need harnesses or sections thereof, he makes those too! (IMG:style_emoticons/default/beerchug.gif)

http://bowlsby.net/914/Classic/TechNotebook.htm
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bbrock
post Jan 31 2018, 06:59 PM
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QUOTE(doug_b_928 @ Jan 31 2018, 05:49 PM) *

Brent, I think I'll have to study your posting for 2 weeks before I understand it (IMG:style_emoticons/default/smile.gif). It's great to know you've been through this. I can tell you are much more knowledgeable than me so you might have to dumb down your advice to beginner level so that it doesn't go over my head.


I'll be revisiting mine based on Jeff's wire gauge comment. I used the '74 diagram to decide wire sizes. Whoops!. I didn't really like the look of the thin-wall wire anyway, but will probably use it again with heavier gauge.

So, GXL and TXL. I didn't know about these until I researched for my harness. These are the two wire types that are automotive grade and what you want to look for if you buy wire. TXL is more modern with thin-walled insulation. Easier to pull through sheathing but looks skinney compared to to the same gage wire in the harness. GXL has thicker insulation like the old factory wire.

BTW, I had the same reaction as you looking at the harness at first. But after you spend a little time with it and your dagrams, it starts looking pretty simple.
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earossi
post Jan 31 2018, 08:23 PM
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QUOTE(mepstein @ Jan 31 2018, 06:21 PM) *

QUOTE(earossi @ Jan 31 2018, 07:15 PM) *

There is a guy over on the Pelican Engine Rebuilding forum who has a cottage business going to fabricate new Porsche wiring harnesses. He's done tons of these and feedback on the forum is extremely good. Not very expensive either.

What’s his name?


His forum name on the Pelican Engine Rebuilding forum is "timmy2". His name is Dennis. You should be able to get to him via PM or email.

He has created replacement harnesses for a number of Porsche models. If he does not have the pattern, you just need to send him your old harness and he'll provide a proper replacement with the correct connectors. And, he is reasonable.
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mepstein
post Jan 31 2018, 08:49 PM
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QUOTE(earossi @ Jan 31 2018, 09:23 PM) *

QUOTE(mepstein @ Jan 31 2018, 06:21 PM) *

QUOTE(earossi @ Jan 31 2018, 07:15 PM) *

There is a guy over on the Pelican Engine Rebuilding forum who has a cottage business going to fabricate new Porsche wiring harnesses. He's done tons of these and feedback on the forum is extremely good. Not very expensive either.

What’s his name?


His forum name on the Pelican Engine Rebuilding forum is "timmy2". His name is Dennis. You should be able to get to him via PM or email.

He has created replacement harnesses for a number of Porsche models. If he does not have the pattern, you just need to send him your old harness and he'll provide a proper replacement with the correct connectors. And, he is reasonable.

I know he does engine harnesses for 6’s. I didn’t realize he did chassis wire harness.
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doug_b_928
post Feb 3 2018, 12:47 PM
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So, using my spare harness pieces, I found the matching wire and what I think would be the proper housing for the oil temp sensor and installed it (can be seen in the pic below, barely, sorry). I've also put together a plan for the fuel pump wiring. As you can see, I salvaged one of those double housings and the proper connectors. In the pic below everything is just mocked up. I'll solder the wires with the male spade connectors, then install the housing and use female spade connectors with double wires. The double is so I can bring the original fuel pump connector back from the farm and install it on one pair (in case I ever want to install a pump in the original location) and then the other pair will have 12G wires attached that will be run up to the front of the car. I'm doubtful about getting the pair of wires in the small sheath for these wires, but I think I can get them through the shorter piece of sheath that goes up the firewall and has the snorkel around it. Would the edges on a coat hanger be too sharp to push through the sheath for pulling the wires? Anyone see any problems with this plan?

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Dave_Darling
post Feb 3 2018, 01:29 PM
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A coat-hanger will poke through the snorkel. If you round the end carefully, it might not--not sure. The snorkel on my car has a couple of holes in it...

I wouldn't bother running the ground myself. A ground is a ground, so just running a wire to some fastener going solidly into the chassis should be fine. Or adding one of those Y connector things to an existing grounding lug.

--DD
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bbrock
post Feb 3 2018, 02:27 PM
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QUOTE(Dave_Darling @ Feb 3 2018, 12:29 PM) *

A coat-hanger will poke through the snorkel. If you round the end carefully, it might not--not sure. The snorkel on my car has a couple of holes in it...

I wouldn't bother running the ground myself. A ground is a ground, so just running a wire to some fastener going solidly into the chassis should be fine. Or adding one of those Y connector things to an existing grounding lug.

--DD

(IMG:style_emoticons/default/agree.gif) Just route a brown wire from the new pump location whatever ground is easy and pleases you. Shorter is better anyway. On my car, there was a length of sheathing in the front trunk that was split and wrapped with ~1/2" wide vinyl electrical tape. I you want to run your wire through there and have trouble, you can just remove the tape, run the wire, then rewrap it and you'll never be able to tell you were in there. I bought some narrow tape on ebay, but I doubt you'd ever notice if you just used regular stuff.
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JeffBowlsby
post Feb 3 2018, 02:47 PM
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Umm...

The 1975-76 schematic indicates that the FP CIRCUIT runs from the 14 pin connector (pin 13) to the fuel pump and needs to be 12 gage, presumably due to the ampacity requirements for that condition. You are leaving half of that circuit as 16 gage, splicing on a 12 gage section. Seems to me that the 16 gage section will be subject to overload and is a fire hazard if it overheats.

Now I know we are going to hear the masses chime in and say they just ran 16 ga lamp cord to the front trunk with no problems. What would an EE's say if (s)he were to anlayze/engineer the loads/distance of that circuit?
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doug_b_928
post Feb 3 2018, 03:17 PM
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Hmmm...So you're suggesting to pull the FP wire out of the 14 pin connector and add a 12G in it's place. Are those ends that fit in the 14 pin connector still available? I have a spare 14 pin connector with wires in it, is it possible to pull one of those ends off of a wire and crimp it onto my new wire?

Per Dave and Brent, I'll forego the ground and either connect directly to the chassis or find an existing ground close by.
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bbrock
post Feb 3 2018, 03:22 PM
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QUOTE(doug_b_928 @ Feb 3 2018, 02:17 PM) *

Hmmm...So you're suggesting to pull the FP wire out of the 14 pin connector and add a 12G in it's place. Are those ends that fit in the 14 pin connector still available? I have a spare 14 pin connector with wires in it, is it possible to pull one of those ends off of a wire and crimp it onto my new wire?


You can reuse those pins. They are just soldered on. I unsoldered all of mine off the 14-pin connector just to make it easier to insall new sheathing. Just secure the pin somehow (I used a "helping hands" soldering station) and tug gently on the wire as you heat the pin with the soldering iron. When the solder melts, the wire will pop right out. Jut reverse to reinstall.
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doug_b_928
post Feb 3 2018, 03:24 PM
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Awesome Brent, thanks!
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