Wiring question 86 911 ignition to starter

[Yan2947]

Trying to follow the Large Yellow #50 wire from the ignition to give power to the starter solenoid. I've had to re-wire my car - it was a burnt out interior and doing an engine swap. When I tested a large wire that I believe to be headed to the starter I only get 5.4 volts - not 12v. I may be wrong about the wire but it comes from a branch as pictured with two wires coming in and two going out (first 2 photos). My ignition has only 1 yellow wire at #50. As described in SpiderMike's post:

https://forums.pelicanparts.com/porsche-911-technical-forum/854546-understanding-ignition-switch.html

the only difference is the yellow wire at "R" is not yellow on my 86 but green (as pictured in the 3rd photo probably because my 86 is a late year build with 87 wiring perhaps).

Is there somewhere I can trace the yellow wire out of the ignition. It goes into the bulkhead and into the large wire loom but other than my first two photos not sure if that is the wires. Also not sure what type of connector is shown in the first two photo. I think a wire goes into the smuggler's box to deal with shutting AC off when cranking as picture in the 4th photo. Perhaps Timmy2 or Spidermike can chime in.

[wazzz]

Being built late 86 your car is a MY 87, as shown by the green wire that indeed appears starting this year. So you should be following wiring diagrams for 87, not 86. Do you have them? If not drop me your email by PM and I can send you a zip file with all factory diagram JPG files for this year. They are zoomable and easy to follow. They are in English except for wires colors which are labeled in German, so you need to look for GE (meaning yellow in German).

The connector you are showing appears on the diagram with four branches like yours.
You need to look for a welding point, as shown on this pic where I'm showing all branches for circuit 50. This is for MY 87. Circuit R from ignition switch is a green wire as you can see.

[Yan2947]

Is it possible that my first two photos are where you have "to heater lever contact" directly above that? I'm not sure I understand the welding point you mention. I would assume a welding point is for ground? I must be wrong on that just looking at the color of the wires... And does that connection point in my first two photos do anything other than make connection or is there something else in there? I sent you pm with my email.
thanks!

[wazzz]

I sent you the factory diagrams. The plastic transparent connector you are showing in your first two pictures appears to be what is called WIRE BRANCH on the diagram. Two wires in, two wires out, all tied together. You are looking to trace the bigger wires that are 4.0mm2. One is apparently coming from the ignition switch via a six pin connector, the other one leaving the transparent connector is going to this welding point, then from there to the starter solenoid, still in 4.0mm2 gauge.
Welding point is what they call it on the diagram (not shown on this screen cap, but you'll find it on the full picture), but it may be better called solder point or whatever is a bunch or wires soldered together, and of course wrapped and isolated from ground. I don't know where to find this.

[Yan2947]

With the two photos below, and a voltage tester, using the two wires that come off of the top of my first two photos in this post, there is no voltage when the key is off to either of those two wires. When the key is in the on position then I get approximately 5.7 volts and when I put the key in the crank position I get just over 12 volts. Is the 5.7 volts normal in the on position. I believe these are the starter solenoid wire (the thicker one) and the thin one with the tester attached originally went to the dme perhaps.

[SpyderMike]

PM sent. Wazzz has identified the location on the schematic...is the outstanding question - what should the voltage be on the starter wire in the key's "off" position?

[Yan2947]

I think I solved it, but I won’t know until I get a new relay. I unplugged the relay in the smuggler box for the AC blower. That is somehow connected to the ignition so that when you turn the key to crank the air conditioner, blower is off While in crank position. When I removed that plug, I found that in the run position, there was no voltage on the wires and in the crank position, the yellow wires were 12 V so I am hoping that a new relay will do the job.

[Yan2947]

Hopefully, I will be able to get this thing running one of these days.

[Yan2947]

And a very tight fit!

[wazzz]

Originally Posted by SpyderMike

PM sent. Wazzz has identified the location on the schematic...is the outstanding question - what should the voltage be on the starter wire in the key's "off" position?

Exactly! With a high impedance voltmeter or tester, you get all sorts of meaningless voltage values when measuring various points of a floating circuit that is not powered. I never care to test voltages in this situation.
If 12V is present at the starter solenoid when cranking, that's fine. Once the fat yellow wire will be connected to the starter solenoid, the voltage will be zero when key is off as any stray voltage will be shorted to ground through the solenoid coil.

[Yan2947]

Gilles, I put in a new relay for the AC blower, hoping something there would get rid of the problem of stray volts. Same exact 5.9 volts in the run and 12 volts in the start (crank) position of the key. Are you saying do not worry about the 5.9 bolts? Once it is connected to the solenoid, it will have no effect?

[wazzz]

Yes, connect the wire to solenoid. That stray voltage is only present when ignition key is on, right?
Not when key is off.

[Yan2947]

It is off in the on position like accessories and it is on in the run position and it is on in the start or crank position. In the run position it is approximately 5.6 V and in the crank position, it is approximately 12 volts. And yes, there is no voltage in the off position.

[timmy2]

As per my reply to your PM, the 5 volts is a result of the A/C wiring design by Porsche using the starter solenoid as a ground to the A/C system.

[Yan2947]

Thank you all for the help. I will proceed as suggested and not worry about the 5 V.