1968 The purple wire

[franklinair]

I'm repairing/re-wiring the dash harness in my CS. (Arlie warned me!)
I cannot identify the purpose/function of the purple wire coming out of the ignition switch connector.
There are a total of 6 wires @ the connector:
Yellow (21) to factory splice, then to (37) alternator & (25) to HL switch
Pink (16A) resistance wire for coil
Green/red (904) to Voltage regulator
Red/blu (32) to Neutral switch
Black/grn (297) from fuse panel
Purple ????:undecided

Any ideas?

Neil

 

[CougarCJ]

Mine is next to me in a drawer, no purple wire on my ignition plug.

 

[franklinair]

On my car the original harness has this purple wire. The used original harness I purchased also has the purple wire.

Neil

 

[CougarCJ]

Looked in our 1968 Ford Electrical manual under Mustang.

21 Yellow
297 Black - Green
16A Pink
904 Green - Red
32 Red - Blue
37B Black - Yellow

 

[dalorzo_f]

Ford docs are notorious for errors... many of the wiring diagrams have wrong colors/references. Some have numbers on wires that don't even show up in the legend on the drawing! :wink:

On the road and have a color coded wiring plan I did off my 68's. Will check to see what that purple wire is, if it showed up. Tach and fogs, GT/non-GT did make a difference on some of the wiring, don't think the connector area was one but will look....

 

[franklinair]

Seems strange; 2 separate cars having the same anomaly with the purple wire. I have a printout of all wires (color code & wire number, plus circuit function) for 1965 thru 1973 models. This purple wire doesn't show up anywhere, and certainly not in the wiring diagrams.
Last resort would be to split the wrapped wiring bundle and physically trace the wire.:sad:

Neil

 

[CougarCJ]

Why can't it be traced on the electrical diagram? Which position in the plug is this purple wire of yours?

 

[Mosesatm]

Here's a thread from another site.
http://forums.vintage-mustang.com/concours-forum/567470-ignition-switch-wire.html

 

[franklinair]

Here's a photo of the ignition switch connector showing the purple wire. This is an original, undisturbed harness.
The connector in the car is identical. Wiring diagrams do not show this wire or function.

Neil

 

[Mosesatm]

Is there any power to it?

 

[franklinair]

No power applied, battery disconnected- until I complete 'cold' checks for all wiring/circuits. (A practice left over from aircraft experience.)

Neil

 

[rvrtrash]

From what I can find, the purple wire is the "Prove Out", which is active when the ignition switch is in the "Start" position. It provides a ground for the brake warning indicator in the dash, to illuminate the bulb and show it's functioning.

Steve

 

[franklinair]

I KNEW someone here would figure this out. (Most likely....Steve):smile:
Which also brings to mind: Scott said his harness does not have this mystery wire. How come?
I'm going to an 'airline cronie' reunion this weekend. When I'm back Monday I'll check & verify the circuit to the brake warning light. Thanks Steve.

Neil

 

[dalorzo_f]

The main wiring diagram calls it out as "Violet" and it runs thru a red connector to the "Chassis Differential Switch".

 

[dalorzo_f]

Looked at the fried harnesses out of the '68 S GT coupe and the violet wire goes to the red connector thru the firewall to the engine harness. Jumps to a violet/white past the connector and dissappears into the harness, a quick look did not show where it went and did not chase continuity...

 

[rvrtrash]

I KNEW someone here would figure this out. (Most likely....Steve):smile:
Which also brings to mind: Scott said his harness does not have this mystery wire. How come?
I'm going to an 'airline cronie' reunion this weekend. When I'm back Monday I'll check & verify the circuit to the brake warning light. Thanks Steve.

Neil

You can thank me when and if, I'm proven correct. The prints and info on it aren't real clear. More of a "reasonable doubt" sort of guess than a solid proof.

Steve

 

[x-codegtcs]

My AMP repro wire harness also has the purple wire. I looked through my Jim Osborne wiring diagram and it shows the violet wire (977) and it connects to a red wire (63) to the wiper switch and then to the motor...maybe I am reading it wrong. I will get a photo of the diagram and highlight the route and where it shows the splice.

 

[x-codegtcs]

Here are the wiring diagram images...hope this helps.

 

[dalorzo_f]

Hard to read, but I think you misread the diagram, on mine it is faint but it looks like where you T the wire to the left to the switch it actually goes down to the bottom of the page and to the left into the "Chassis switch"... at least it looks that way on mine... otherwise the drop to the 977 to the DTL red connectors noted comes out of nowhere...

???

 

[x-codegtcs]

Hard to read, but I think you misread the diagram, on mine it is faint but it looks like where you T the wire to the left to the switch it actually goes down to the bottom of the page and to the left into the "Chassis switch"... at least it looks that way on mine... otherwise the drop to the 977 to the DTL red connectors noted comes out of nowhere...

???

Richard, you are right. If I go down half an inch there is a line them materializes out of nowhere. So as you mentioned earlier it 977 goes to the chassis differential switch - whatever that is - and then up to the instrument cluster to the "Dual Brake Warning" light - so the "Whatever" must be the brake pressure differential switch as I call it...I have never heard it called the chassis differential switch...so full circle to Steve who commented it being the prove out (labeled as PO in the diagrams) for the brake warning light.