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Technical discussions specific to 1964-1967, 1968-1970, and 1971-1973 Classic Mustang. Discuss all tech related to in-line six cylinder and V8 powered Vintage Mustangs here.

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Unread 02-25-2009   #1 (permalink)
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Default 1967 Ignition Wiring Harness

I recently purchased an engine harness cable to replace the hacked into and cracked harness. I didn't pay attention that the hacked into cable had a brown wire wired into the coil wire on the harness. I chased that brown wire through the firewall and found that it attached to the ignition switch.

I have the 67 Ford Repair Manual, but it does not present a clue about my problem. My ignition switch has this square (Circuit, Resistor) what ever it is at the rear of the ignition switch. There appears to be a center post with a galvanized bar attached to it that this (Circuit, Resistor) unknown thing is attached to.

It is a small box, maybe 3/4" in length and 3/4" in width, that has two posts on it. One post is marked yellow and other is red. The hacked into engine cable or additional brown cable is attached to the yellow post on the small box.

I tested the new cable, the car will turn over and appears to start, but will die once I let go of the key turned to start the car. When I put the hacked into cable back in place the car starts and runs fine. I was hoping to return the wiring to original, but I'm lost at this point.
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Unread 02-26-2009   #2 (permalink)
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In my wiring diagram for a 67 ignition, starting, and charging systems, there is only 1 brown wire. It goes from the starter motor relay on the 3rd post away from the battery. It ends up at a 4-prong square shaped connector. There are 2 wires on the other end of the connector that are continuations of the brown wire. They are red/green stripe. The first red/green wire ends up at the coil. The second red/green wire has 2 end points after the firewall. The first end goes to a resistor and then to the tach. The second end is at a resistor connected to the ignition switch.

So, as far as my diagram is concerned, in the ignition and charging system the brown wire and the red/green stripe wires are the same.

If you tell me what wires are in the new harness, it may help out a bit. You can PM or email me.
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Unread 02-26-2009   #3 (permalink)
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Hi Jeff,

Hope the attached schematics help you trying to find out what that brown wire is for.

My understanding is that the brown wire comes from the engine bay (starter solenoid terminal I) and once you disconnect it, your car has no "spark" to keep running.
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File Type: pdf 67 Mustang Wiring Schematics (starting system).pdf (381.7 KB, 1823 views)
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Unread 02-26-2009   #4 (permalink)
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Default More Information Please

Notice the white arrow on the attachment points to the device I have no clue about. It appears to be attached to the center post on the rear of the ignition with an adapter. There are two additonal wires attached to the center post as well.

What is this for?

Notice the yellow arrow points to the brown wire attached to the unknown device, is fed through the firewall and is spliced into the main engine harness cable on the red/green stripe wire, which ends up on the coil.

My replacement engine harness cable came from Mustangs Unlimited, it's a 3 prong connector, two male, one female.
Female = Red/White Stripe to Oil Sender
Middle Male = White/Red Stripe to Water Temp Sender
Outer Male = Red/Green Stripe to Coil

I must investigate further to check that the original brown wire, which should be coming from the SMR does indeed come back to the ignition through the 4 prong connector. I believe that ends up as a Pink color, which I see is attached to the ignition.

Thanks for the tips!
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1967 Ignition Wiring Harness-67-ignition-rear-view.jpg  
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Unread 02-27-2009   #5 (permalink)
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The small box appears to be a circuit breaker. There should be a marking on it to designate the amperage rating. The PINK wire should be the resistor wire that reduces the voltage to the coil when the ignition switch is in the run position. It's connected to the RED GREEN STRIPE wire that then leads to the coil from the back of the 4 pin connector and then through a 3 pin connector.

When the ignition switch is in the start position, the resistor wire is bypassed so that the coil receives a full 12 volts to assist in the engine starting. For some reason the previous owner must have installed the circuit breaker for some kind of circuit protection. This is not an original installation and doesn't belong in the circuit.

The BROWN wire should transition into two RED GREEN STRIPE wires at the back of the 4 pin connector. One should lead to the coil (Through the 3 pin) and the other to the PINK resistor wire, then on to the ignition switch. The BROWN wire originates at the rear most small terminal on the starter solenoid and is energized only when the ign. switch is in the start position and the solenoid is activated. The BROWN wire's only purpose is to deliver the full 12 volts to the coil when the starter is engaged and the ign. switch is in the start position. It should not be connected to the ign. switch itself. It should only run to the 4 prong connector.

The center post on the back of the ignition switch is the accessory terminal and is hot only in the run or accessory positions.
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Unread 02-27-2009   #6 (permalink)
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Thanks for solving the puzzle... Now I have a chance at restoring it back to the original wiring, once I go further and investigate the SMR side. Obviously, when I tried the new cable I'm having some sort of short, no power, since the Pink wire is attached to ignition.

I'm so glad I posted and recieved this help!!!

I'll come back to the post and reveal my findings.

Thanks again to all who posted!
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