yellow wire rewiring

[chamilun]

hello to all,
Ive searched and searched and not found a good write-up for replacing the yellow wire from the ignition to the starter.

anyone have any tips, or point me in the right direction?

thanks

82 sc

[steely]

this help?

Anyone replaced the starter yellow/signal wire? Please help.

[chamilun]

wow, nice link. Looks like this may be a PITA, but a necessary evil.

[john walker's workshop]

why? melted?

[boyt911sc]

Originally Posted by chamilun

hello to all,
Ive searched and searched and not found a good write-up for replacing the yellow wire from the ignition to the starter.

anyone have any tips, or point me in the right direction?

thanks

82 sc

chamilun,

The yellow wire from ignition switch (@terminal #50) to starter is divided into 2 sections. The first section is from ignition switch and end up at terminal #1 chassis side (14-pin connector located in the rear fuse panel). The second part is from terminal #1 (engine side) going to the starter. In summary the first section is found in the car body wire harness and the second section is in the engine wire harness. The first and second section is connected by pin #1 (14-pin connector).

So my question to you is what's the problem with the yellow wire? Have you confirmed which is the problematic section? PM me and I'll provide you with a detailed and step-by-step procedures to test the wire/s and I might have some pictures too.

Tony

[chamilun]

Problem is car does not start after warming up. This seems to be a somewhat common problem after doing a good bit of research. The current drops after the wire heats up. I can bypass (long wire out door to under car) and starter engages no problem.

boyt911sc (Tony), Id appreciate a PM with all that info. I plan to track down what section is at fault, but Im assuming its the engine side (?)

thanks for all the help. awesome forum

[chamilun]

Tony,
your PM box is full as well, so can't send you anything

[dsmyth]

Its interesting to see this post because my 85 has had the yellow wire replaced with a blue wire going back to the starter following the harness by previous owner. I started to have intermittent starting problems and bypassed the blue wire from under my seat to the ignition which has solved the problem for now. I would like to fix the wiring and return it to stock color and setup. The engine is currently out for a reseal and now I have access to the wiring harness. Can you share any ideas you might have on the subject as electrical is not my best strength. thanks Doug

[john walker's workshop]

be sure the battery to body ground is clean and tight as well as the trans to body ground. starter solenoids get hot and don't work until they cool down. normal problem. replace the starter/solenoid as a unit. nothing wrong with the yellow wire.

[chamilun]

I guess when you have over 11k posts, you can say something like this with such definity. But youre incorrect, at least sort of, but thanks for the suggestion

Problem found! The 14 pin connector on the drivers side behind the plastic cover where the fuses are had very loose connections. The yellow wire coming from the chassis side has two yellow wires that join into the connector. This makes it too thick and more difficult to get a complete connection. Not figuring out a way to get it seated deaper, I simply took the two sides out of the plastic adapter setup, am plugged them in directly so that they seat perfectly.

One way to diagnose this potential problem if your starter is not clicking at all is to run a wire from the yellow wire to the live fuse. If you starter engages, as mine did, the problem is forward of that point.

thanks for all the help

Originally Posted by john walker's workshop

nothing wrong with the yellow wire.

[john walker's workshop]

well, the wire was fine right? it's usually the connections on the ends that are the problem.

[NOLAsc]

Originally Posted by chamilun

Problem found! The 14 pin connector on the drivers side behind the plastic cover where the fuses are had very loose connections. The yellow wire coming from the chassis side has two yellow wires that join into the connector. This makes it too thick and more difficult to get a complete connection. Not figuring out a way to get it seated deaper, I simply took the two sides out of the plastic adapter setup, am plugged them in directly so that they seat perfectly.

One way to diagnose this potential problem if your starter is not clicking at all is to run a wire from the yellow wire to the live fuse. If you starter engages, as mine did, the problem is forward of that point.

"run a wire from the yellow wire to the live fuse..."
Is this jumper test all done at connections under the plastic cover left of the engine -- from the yellow at the 14-pin connector to a live fuse near there? Or is it done from the yellow wire at the starter to a live fuse in the trunk or engine compartment?

Reason for asking: Once again battling inopportune non-starts -- seems to happen more on short trips, when the engine is not fully warmed up. Checked and cleaned the usual suspects -- all connections on battery and starter sides. Recharged the battery. Sometimes starts fine (after driving 20 minutes or more); other times, if I hold the key to start for uncomfortably longer than I should, it cranks right up.

Thanks,
Shawn

[NOLAsc]

Oh... checked voltages and voltage drops all over the place. Doesn't seem to drop a lot on "start" from ground to starter. Maybe less than a volt on my old analog meter. That may be just the fuel pump or whatever else gets activated in the start position.

[NOLAsc]

Originally Posted by NOLAsc

"run a wire from the yellow wire to the live fuse..."
Is this jumper test all done at connections under the plastic cover left of the engine -- from the yellow at the 14-pin connector to a live fuse near there? Or is it done from the yellow wire at the starter to a live fuse in the trunk or engine compartment?

Reason for asking: Once again battling inopportune non-starts -- seems to happen more on short trips, when the engine is not fully warmed up. Checked and cleaned the usual suspects -- all connections on battery and starter sides. Recharged the battery. Sometimes starts fine (after driving 20 minutes or more); other times, if I hold the key to start for uncomfortably longer than I should, it cranks right up.

Thanks,
Shawn

Nevermind. I'll figure it out. Not rocket science. BTW, car started pretty flawlessly today.

[Bob Kontak]

NOLA - There are 911SC wiring diagrams in the Tech Info Center - see tab up top on this page.

They will come in handy across time.

[chamilun]

from the yellow at the 14-pin connector to a live fuse near there

you got it. simply separate the yellow wiring and apply 12 volt at the nearby fuse block

[NOLAsc]

thanks.

[Grady Clay]

Now that the problem is identified, let’s review.

Using a separate wire from the battery to terminal #50 at the starter is a good diagnostic to identify the problem.
Additionally, having a voltmeter at terminal #50 at the starter during cranking (or attempt) is also a good diagnostic.
Further diagnostics can be measuring the voltage at various points in the circuit while cranking (or attempt).
Keep in mind that a voltage drop only occurs when there is current flowing during cranking (or attempt).



Considering an ’82 911SC (applies to many more):
(This is from my “Current Flow Diagram Type 911 SC USA Model 82”, Sections I –III, p.p. 01-3/89 through 01-3/93.)
Pelican Parts - Porsche 911 Parts Listings & Diagrams seems to be identical.


The ‘yellow wire’ has a number of connections between the battery B+ and the starter #50 terminal.
First are two of the three red wires at the B+ terminal at the battery.
These are the two 4.0 mm red wires in parallel (the third is a red 6.0 mm wire).
The connection between the wires and the B+ clamp connector are often neglected.

The two 4.0 mm red wires in parallel go to terminals #2 & #3 of connector T6f.
This is a 6-pole connector below the instrument panel.
After this connector, the two red wires are smaller 2.5 mm and terminate at terminal #30 at the ignition switch connector.
There is a third 2.5 mm red wire at terminal #30 that carries current out to the headlight switch and other.

In the electrical part of the ignition switch, there is a contact made from terminal #30 to terminal #50 when in the 'START' position.
The ‘yellow wire’ (2.5 mm) starts here (terminal #50).
The yellow 2.5 mm wire goes (again) through connector T6f, now pin #5. After the connector the yellow wire becomes 4.0 mm.

This 4.0 mm yellow wire now goes to 1-pole connector T1e on the luggage compartment floor.
The ‘downstream’ side of this connector has the 4.0 mm yellow wire continuing to the rear of the car in the main harness. There is also a yellow 1.5 mm wire to the fuel pump relay.

At the rear, the 4.0 mm yellow wire goes to terminal #1 of T14 – the 14-pin connector for the engine. Going into this connection, there is also a 0.5 mm yellow wire to supply power for the switch and relay for the heater blower at the engine.
After terminal #1 of T14 – the 14-pin connector for the engine - the yellow wire becomes 2.5 mm and goes through the engine wiring harness to terminal #50 at the starter motor solenoid.


As you can see, there are a total of six! connections plus the contacts in the ignition switch just to get power to the starter solenoid.
In addition, there are contacts in the solenoid assembly, a ground strap (two connections) between the transmission and the chassis and the ground strap (two connections) at the battery.

There is a lot of opportunity for mischief here.

Best,
Grady

[oneblueyedog]

I considered the rewire. Installed a Hi torque instead. For 8 years the problem has been solved. The yellow wire lore was a total waste of time and money for me. Don't get sucked in.

[NOLAsc]

Originally Posted by Grady Clay

Now that the problem is identified, let’s review.

Using a separate wire from the battery to terminal #50 at the starter is a good diagnostic to identify the problem.
Additionally, having a voltmeter at terminal #50 at the starter during cranking (or attempt) is also a good diagnostic.
Further diagnostics can be measuring the voltage at various points in the circuit while cranking (or attempt).
Keep in mind that a voltage drop only occurs when there is current flowing during cranking (or attempt).



Considering an ’82 911SC (applies to many more):
(This is from my “Current Flow Diagram Type 911 SC USA Model 82”, Sections I –III, p.p. 01-3/89 through 01-3/93.)
Pelican Parts - Porsche 911 Parts Listings & Diagrams seems to be identical.


The ‘yellow wire’ has a number of connections between the battery B+ and the starter #50 terminal.
First are two of the three red wires at the B+ terminal at the battery.
These are the two 4.0 mm red wires in parallel (the third is a red 6.0 mm wire).
The connection between the wires and the B+ clamp connector are often neglected.

The two 4.0 mm red wires in parallel go to terminals #2 & #3 of connector T6f.
This is a 6-pole connector below the instrument panel.
After this connector, the two red wires are smaller 2.5 mm and terminate at terminal #30 at the ignition switch connector.
There is a third 2.5 mm red wire at terminal #30 that carries current out to the headlight switch and other.

In the electrical part of the ignition switch, there is a contact made from terminal #30 to terminal #50 when in the 'START' position.
The ‘yellow wire’ (2.5 mm) starts here (terminal #50).
The yellow 2.5 mm wire goes (again) through connector T6f, now pin #5. After the connector the yellow wire becomes 4.0 mm.

This 4.0 mm yellow wire now goes to 1-pole connector T1e on the luggage compartment floor.
The ‘downstream’ side of this connector has the 4.0 mm yellow wire continuing to the rear of the car in the main harness. There is also a yellow 1.5 mm wire to the fuel pump relay.

At the rear, the 4.0 mm yellow wire goes to terminal #1 of T14 – the 14-pin connector for the engine. Going into this connection, there is also a 0.5 mm yellow wire to supply power for the switch and relay for the heater blower at the engine.
After terminal #1 of T14 – the 14-pin connector for the engine - the yellow wire becomes 2.5 mm and goes through the engine wiring harness to terminal #50 at the starter motor solenoid.


As you can see, there are a total of six! connections plus the contacts in the ignition switch just to get power to the starter solenoid.
In addition, there are contacts in the solenoid assembly, a ground strap (two connections) between the transmission and the chassis and the ground strap (two connections) at the battery.

There is a lot of opportunity for mischief here.

Best,
Grady

Grady, as always, thanks for sharing your expertise. That post will be very helpful -- to me as well as a bunch of other people here.

Originally Posted by oneblueyedog

I considered the rewire. Installed a Hi torque instead. For 8 years the problem has been solved. The yellow wire lore was a total waste of time and money for me. Don't get sucked in.

Thanks oneblueye. You may be right. But I've gotta make what I have last as long as it can before throwing more money at it. My project list with our host always exceeds my open-to-buy level.

Shawn