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Discussion Starter #1
Hi All,

I am helping a friend fix the wiring in his 1973 Mach 1 with 351C. The alternator harness was butchered to point we ordered a new one and the wiring that goes to the alternator harness and starter solenoid is presently being worked on/repaired. We found the stub of the white/black stripe sticking out of harness for example.

First question, I am having trouble identifying the correct location to hookup the pale orange wire annotated with the red arrow coming from the harness at the bottom of the passenger side fender apron. Another picture attached shows it with a red circle.

So far it appears the location for the other wires are as follows:
black with orange stripe goes to the distribution terminal on firewall.
Wires with green annotation circle go to the front posts on starter solenoid.
Wires with blue annotation (yellow, green/red stripe, white/black stripe) go to the alternator harness
Yellow wire on alternator harness goes to terminal on left side of starter solenoid.
Black with orange stripe on alternator harness goes to the terminal on firewall.


mach-w1.jpeg
mach-w3.jpg




Second question, what wire part #'s do I need to hook into the two plugs at the firewall behind engine? Picture attached.


mach-w2.jpeg
 

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Link to 73 Mustang wiring diagram


One of the the two flat rubber plugs by the firewall is for the engine gauge harness. The other is usually for accessories such as A/C clutch and emissions.
 

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Discussion Starter #3
Wiring book is not helping, nor are images from Google, nor are countless searches.

If anyone can help with a description of where the pale orange wire annotated above attaches to it would be a big help. Also, what wiring I need to purchase to go from ignition coil to firewall.
 

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Wiring book is not helping, nor are images from Google, nor are countless searches.

If anyone can help with a description of where the pale orange wire annotated above attaches to it would be a big help. Also, what wiring I need to purchase to go from ignition coil to firewall.
I believe your pale orange wire is actually yellow, which is the primary power feed to the fuse box, it attaches to the Batt (+) stud on the starter solenoid.

You'll need the 14289 gauge feed harness. NPD shows out of stock on the manual trans version, so here is one from Kentucky Mustang


Auto harness on NPD

 

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Discussion Starter #6
I believe your pale orange wire is actually yellow, which is the primary power feed to the fuse box, it attaches to the Batt (+) stud on the starter solenoid.
I do know there is a yellow wire (with similar terminal loop) on the alternator harness that attaches to the left positive (+) battery stud looking at the starter solenoid.

Are there two wires that attach to that starter solenoid stud in addition to the battery cable?

(That pale orange wire I am looking for a location to is coming from the wiring at the bottom of the fender apron, not alternator harness as I mentioned.)

Are there any wires that ground to one of the two voltage regulator mounting bolts?

Auto harness on NPD

Thanks! This is a '73 351C with automatic transmission!

Wow, I now have no idea what those 6 (or more) plugs attach to on that harness.
-Ignition coil
-Temperature sending unit
-Oil pressure sending unit
-?
 

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I do know there is a yellow wire (with similar terminal loop) on the alternator harness that attaches to the left positive (+) battery stud looking at the starter solenoid.

Are there two wires that attach to that starter solenoid stud in addition to the battery cable?

(That pale orange wire I am looking for a location to is coming from the wiring at the bottom of the fender apron, not alternator harness as I mentioned.)

Are there any wires that ground to one of the two voltage regulator mounting bolts?
Does this car have gauges? Where the wires go varies depending upon gauges or not.


Terminal Block - Yellow/White dots (from alt harness) Black/Orange stripe (from main harness) & Black/Orange stripe (from alternator harness) , circuit breaker for Auxiliary Power feed harness (power windows, rear defrost)

Starter solenoid batt (+) lug - Batt (+) cable, Yellow (fusible link -from main harness) "Orange" wire on your harness

Starter solenoid "S" terminal - Red w/light blue stripe (wire w/yellow ring terminal on your harness)

Starter solenoid "I" terminal - Red w/light green stripe (wire w/green 90° boot and yellow heat shrink on your harness)




Thanks! This is a '73 351C with automatic transmission!

Wow, I now have no idea what those 6 (or more) plugs attach to on that harness.
-Ignition coil
-Temperature sending unit
-Oil pressure sending unit
-?
EGR solenoid
Electric choke
Throttle solenoid
A/C clutch
 

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Discussion Starter #9
Does NPD sell the replacement plugs to repair the factory wire harness (that attaches to alternator harness)? The plug on the white (black stripe) looks hardest to match. Then, one for the yellow and green (with red stripe).


759749
 

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I would contact Midlife Harness Restorations, he probably has that stuff right at hand, or you probably could take a stroll through a junkyard and come up with plenty of candidates.
 

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Discussion Starter #11
Thanks Himikiller!!!

Can you all please help with the color codes for the wires on harness coming from firewall for:
    • Ignition coil
    • Temperature sending unit
    • Oil pressure sending unit
    • EGR solenoid
    • Electric choke
    • Throttle solenoid
    • A/C clutch
 

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Thanks Himikiller!!!

Can you all please help with the color codes for the wires on harness coming from firewall for:
    • Ignition coil
    • Temperature sending unit
    • Oil pressure sending unit
    • EGR solenoid
    • Electric choke
    • Throttle solenoid
    • A/C clutch
Wiring diagram was attached to the post below.

Link to 73 Mustang wiring diagram


One of the the two flat rubber plugs by the firewall is for the engine gauge harness. The other is usually for accessories such as A/C clutch and emissions.
 

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It looks to me like the color code is below the wire number on each page.
For example- on Page 2 in quadrant B1 I see wire #35 with O-LB under it. My best guess is that O-LB stands for Orange with a Light Blue stripe.
 

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Wiring is shown as (circuit # )(base color)(tracer color)(tracer type)

Tracer types are (blank) - stripe, (H) - hash marks, (D) - dots

Example : 175 BK-Y D - circuit 175, black w/yellow dots


Found a color okey in the page below for later vehicles, but the basics are the same.


763208
 
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