engine electrical harness, wire & connector identities

[mcaterino]

Hey everyone,

Posted this yesterday to Pelican, but it seems to have gotten lost in the fascinating 'Por-sha' debate. Answers here aren't critical to me getting my car put back together, but seem worthwhile from a documentation standpoint. The various years' electrical systems aren't all that easy to find clear information on. So, in hopes that this helps, please help me figure out all the connections on this engine harness.
...
As I continue reassembling my car (1970 carbureted T), I've been slogging through getting the electrical system back together. My car came to me with no rear electrical panel or engine harness, so I've purchased used components, none of which are a perfect match for my 1970. The engine harness in particular has a number of what appear to be superfluous (later) components. While I've identified most everything on here, I'd like to confirm a few identities before I begin modifying things (more on this below).

Below is a labelled picture of the harness. See question marks for my uncertainties. Let me mention first that I've perused all available wiring diagrams, and this seems to be from the 71-73 period, for which nothing is easily availble online).

1. The biggest mystery to me now is a small cluster of yellow wires (three yellow wires into two spade connectors, labelled 'O2 sensor?' in the photo) branching off near the starter. I have not been able to find continuity with anything else in the harness. Possibly some emissions sensors?

2. Next to those there's a plug with two minute male spades, and a yellow and red-black wire going into them. This has continuity with the two spaded connectors in the boot (same color wires) near the 14-pin connector. I'm thinking this is a thermo-time switch (colors match) but in all diagrams I've looked at these wires come back through the 14-pin instead of being internal to the harness. I've also read that that type connector is used for warm-up regulators - so maybe a CIS option?

3. There are two voltage regulator connections, (one at the very base, bottom of the harness, one branching nearly opposite the alternator cluster.) I suppose these are alternatives depending on whether an internal or external voltage reg is used. Can anyone confirm? Interesting that the D+ and D- (blue and ground) are on the same spade on the internal connector. (These are also doubled up coming through the normally ground (#12) pin on the 14-pin connector.)

4. Red-white wire next to internal voltage reg plug, single spade connector: Cold-start solenoid on carbs? (On 70 diagram this color matches but is fed from a 'microswitch' whose wire then goes back through the 14-pin.

That's all the indentity questions. Last, I'm planning to go to MSD, and intend to remove the CDI plug, its power lead (2 pin connector close to CDI plug), and the coax/shielded coil and distributor wires (removing all intact by untaping the harness), replacing with new/simple wiring specific to the MSD application, which need not be coax. These coax wires were already poorly modified and would at least need replacement. Any comment?

Thanks,
Mike
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[gruen911]

Mike,
I have a 71T which is as we speak getting a motor installed. The motor coming out is all original. The motor going in is a 73T (rebuilt 2.4S spec) running Webers. I should have the car back by end of the week. I will document the wiring for you once I have some time by the weekend if no one responds with info before then.
BTW, great post. I have always been a little intimidated by the engine bay wiring. Mapping it out like this will be very useful for me, especially since I also have a 2.2T car.

[304065]

This should help, but you've definitely got a "hybrid" harness there--

http://www.pelicanparts.com/911/911_...l_diagrams.htm

On the bottom of the engine tin you have the reverse light switch and the big red and yellow to the starter. The big red doesn't power the starter, rather it carries power from the starter lug back to the engine compartment. That saves weight and complexity over having a separate cable from the battery.

Then it gets complicated. The MFI cars have a cold-start switches installed in the engine oil breather. Some have one switch, some have two. These are energized when the engine cranks, hence the yellow, and they should be in continuity with the Starter solenoid (also yellow).

The double spade connector with the blue and black is the fuel pump.

The alternator is typical pre-74, brown D-, big red B+, black DF, Blue D+/61. Ditto the other end, you have the standard plug on there.

You are right about oil press and temp.

The 2-pin is the power for the CDI, that's also right.

Where it gets weird is the "coax." Coaxial wasn't used until the SC, you should have a standard black/purple to the points and also over to the speed switch. You might start by pulling the tape off that end to see what's going on.

Good luck!

[mcaterino]

I appreciate the help guys. Good to get most of my guesses confirmed. I forgot about them but had checked out the wiring diagrams on pelican for 71 and 73. They didn't really resolve many of the questions, but good to call attention to their availability.

I'm not convinced about the suggestion of fuel pump on the blue + black 2 spade connector. The reason I suggested these are alternate voltage regulator connection points is that there is three-way continuity with these and the blue+black wires at the alternator and at the more conventional (and more conveniently placed) external regulator plug. The 'blue' plug on the two prong connector has a ground (brown) wire (yes, both connected to the same spade), and the two travel together to the 14 pin connector.

Regarding the big red wire from the alternator to the starter, I would presume this is also the route of recharging the battery. Correct?

The whole coaxial question is particularly interesting, especially in combination with the 3 pin CDI connector. Where these meet does in fact look like a respectable factory connection, with the outer shield of both coax wires nicely braided together to join the single spade for the 'D' post of the CD box. The far ends (coil & distributor) though are hacked up. In any case, I'm going to pull all that intact and replace. I don't think anything that remains uncertain is necessary for my application. But there might still be some useful info to come from resolving the questions.

Thanks again. Where I once found all this merely frustrating, now it's both frustrating AND interesting.

Mike

[304065]

Mike, are the pins on the "alternate VR" connection at right angles to one another? If they are, that is the way the pins are set up on the later 55A alternators. Some well-meaning but misdirected PO could have spliced that in without removing the other connection if the alternator were upgraded. Not sure why you would do that vs. changing the ring terminals on the old harness to spade, but nothing surprises me anymore.

Last I checked you can buy a new headshell for the 14 pin connector and the pins are also available but like a buck a piece.

[Sean F]

Mike - my 71T is all original and apart for restoration. What do you want me to take pictures of?

[mcaterino]

A picture of the plug in question is attached. The inner connections are parallel (in line with the wide axis in the picture), relatively narrow (maybe 4mm) spades. However, I retested the continuities, and I jumped the gun on asserting that these connections were all continuous with the voltage regulator. In fact it's only the ground. I should have double checked before. The others I have to check again, I was kind of in a hurry this morning before work.

Next time I get a chance I'm going to start upwrapping and see what things look like inside. I'll report back after I get back from a wedding in the great northern land of cheese.

Also, the 14-pin connector body was in good shape on this, I had just removed it to figure out what was going on inside. I've scrubbed/shined up all these connectors and reassembled it already. But thanks for the suggestion.

Sean, I appreciate the offer of pictures, and I'd be generally interested to see what an unmolested '71 harness looked like. Otherwise I've got all the important stuff nailed down, and will start adapting this clearly molested harness for my specific needs. BTW - I checked out your blog, and it brings back memories (not all that distant, nor all that fond). Good work on the hinge post. I had to do nearly the same thing on my passenger side. Good luck with the rest.

Cheers,
Mike

[304065]

Mike, thanks for the better photo, I figured out what it is, it's a 73-1/2 CIS harness, that extra connector goes to the warmup regulator relay.

[304065]

For a long thread on the delicate interplay between CIS and the charging circuit see here. . . .

http://forums.pelicanparts.com/porsc...ernator-d.html

[cmcfaul]

one of those connectors goes to the radio noise suppression thing next to the CD (Capacitor Discharge) in the engine compartment.

Chris

73 911 E