Rear Engine wiring harness removal

[rekstein1]

I am attempting to replace the rear engine wiring harness that runs from the rear fuse panel in the engine compartment to the alternator. Had anyone done this? Can't seem to find anything related to this in the forum.
Some guidance would be appreciated.

The rear fuse box is off along with the wires and plugs. Is the next thing to take off the ground strap? Its all seems to be shrink wrapped together. Or do I split things out?

thanks Rich
1988 911 cab

[nospiners]

Start by disconnecting the negative battery cable , the removing the alternator to access the harness behind it. You also have to remove the starter cable and the wire to the tranny for the backup lights. Now you can disconnect the plug from the left side of the engine that's attached
to the fuse panel , and pull it through. The brown ground wires that attach to the engine are not a part of that harness

[timmy2]

https://www.pelicanparts.com/More_Info/RD91160701600.htm?pn=RD-911-607-016-00
This is a reference photo of the engine harness that includes the alternator harness. I think you are removing the wrong harness(s)

[rekstein1]

OK, thanks for the info but gonna wait to do anything after posting these photos to take any action as Timmy 2 sugests.

First to recap no power out of pin 3 or 12. this is an 1988 cab so there is no defroster or rear wiper. There was also no power to the rear fuse panel whatsoever.

The first photo showsw the rear end of the engine wiring harness I think someone was in here before and wrapped electical tape up the lengh of the all harness's. Hence why i can't find where the engine wiring harness splits off into the back of the engine. The next photo show the harness wrapped to the ground wire which I believe is from a different harness


But since everything is wrapped together,confusion,hence the confusion to Timmy 2 that he thought i was removing the wrong harness
Following the harness further back is the other harness's going into the back wall
its all wrapped together so I can't see where it splits off to go along the back wall of the engine eventually to the alternator.
Here is a picture of the back wall of the engine where i believe the enginge wiring harness is located somewhere there


Plan of attack
1) wait for you guys to respond
2) remove alternator next and follow wirring back
3) carefully remove the electrical tape of the bundled wiring
4) Drink heavily
5) Ask timmy 2 for the harness

Thanks waiting for your replies

[timmy2]

That is not the engine harness. It is the through body harness from the front of the car.
The engine harness plugs into the one in your hand. It has female terminals in it. Those are male terminals. They will not have power on pins 2 and 14. The power comes from the alternator in the female terminals.
Engine/Alternator harness should be hanging somewhere off the fuse panel side of the engine about 10 inches from the rear engine tin.

[timmy2]

Found a photo and highlighted the engine harness female connector for you, circled in red. Everything on the engine for the alternator is in this harness that is buried underneath most of the fuel delivery intake system.
With battery and starter connected, you should see 12 volts to ground on pins 2 and 14 in that connector. (They are numbered when you look closely)
You will never see 12 volts on the rear fuse panel without that plug connected to the male 14 pin connector in you photo of it in your hand.

[timmy2]

Check for voltage there.
You are not understanding the current flow from battery to starter to alternator then to pins 2 and 14.
Or the harness layout on the engine.
Replacing the engine harness is a major job requiring removal of a lot of the intake system.
There may not be a problem there.
Check for continuity from pin 14 of the male connector to any of the 3 rear fuse panel terminals.(with engine harness disconnected)

[rekstein1]

Glad I waited. Photo was a big help. Went to check and the harness and it is where you indicated. I was confused, but now I understand that the other harness goes to the frunck and realize that that is the main frunk wiring harnessto the rear.
Gonna check the voltage again this Friday on 2 and 14. This is the same connector I checked the first time with no power on 2 and 14. If this is the case, since i see the wire is loose sitting between the fuel rails, the next step would be to remove the alternator and pull the wire through and out.
Correct?

[timmy2]

If battery disconnected. Check continuity from red cable at starter to the pins 2 and 14.
That will tell you if the harness wiring to/from the alternator is bad.

[Billthebuilder]

Definitely remove the fan/ alternator you can see from there where the wires exit the shroud. Then have a beer

[steven c]

My 81 engine is out for a rebuild and the harness is out too, and I just finished cleaning it up. Let me know if you want a pic posted of it for reference?

[wazzz]

A note about your post #4 above. Since you recently opened another thread where you were chasing power at pins 3 and 12 of the heater blower relay socket, make sure you don't confuse these with the 14-pin connector you are holding in your hand.

Here you are chasing power at terminals 2 and 14 of the 14-pin connector, at least that's what I understand. That connector (14 pins) has nothing to do with the heater blower relay socket (only 12 pins).

[spoke]

Here is the engine harness from my '86 930. There is only one harness on the engine and every component is connected to it. This whole thing was located under the intake manifold. I couldn't imagine digging into the harness to replace something w/o removing the engine.

The alternator 12V power on my car only goes to the starter, then on to the battery. Power to any of the fuse panels comes from the battery.

You didn't mention why the harness needed replacing. Are you having issues with something?