Can someone help with wiring?

[pyroman]

I've been doing alot of wiring lately getting set to get the car running after the engine swap. I'm adding in circuits for stuff like MSD, electric fan and a 3G alternator. Adding in the wiring isn't an issue its identifying and reattaching the old wiring.

I have most of the wires identified and located but there are always a few stragglers. Also since I'm adding things like a MSD system (box, coil, dist) and a 3G I figure there are going to be some wires I won't be using, which I need some help ID-ing as well.

Ok, so most of the wires that I'm having problems with are within the headlight wiring harness. So the following are the wires I need ID:

1. Red - part of the front/headlight wiring harness. It "ends" right near the starter solenoid. My thought is it attaches to the positive post of the solenoid, but I don't know what its for. I couldn't find anything in any of the wiring diagrams I combed through.

2. Black, Yellow - These are two wires also part of the front/headlight wiring harness. They also end by the starter solenoid. They both go into 1 ring terminal. What I found was that the yellow wire is #37 in the wiring diagram and eventually goes to the fusebox. I believe the black wire is #152 and goes to the voltage regulator. Since I'm adding the 3G this isn't needed correct?

3. Black - Also part of front/headlight wiring harness. The end of the this wire extends well past the starter solenoid, nearly reaching the firewall. I haven't found any info on this one and have no idea where it goes. My guess would be ground.

4. Black w/orange stripe - Also part of front/headlight wiring harnes. Like the previous wire this extends well past the starter solenoid, nearly reaching the firewall. No info on this one and I have no idea where it's supposed to go.

I'm gonna go snap some pictures so in the meantime, thanks!

 

[2+2GT]

This would be easier if we knew what year your car was. You can find what you need here, though:

Mustang Wiring and Vacuum Diagrams

 

[brianj5600]

I'm guessing it is a 67 by the sig. When I did my one wire, I just unplugged the voltage regulator and pushed the plug through the core support. Everything down there is black and it blends right in. It was not worth it to me to remove a few wires.

Edit: Some of the best money I have spent was for a shop manual. There has been many times I refered to it over the years. Late at night when working and you need an answer it can be priceless.

 

[pyroman]

Oh sorry! Yea its a 67, I meant to put that in the first post. I also do have a shop manual and it has been very helpful to this point. These were the wires that I was unable to find in the digrams given.

Now I have some pics:

The single wire ring terminal up at the top of the picture is the red wire. The double wire ring terminal up at the top of the picture is the black and yellow wires.

The two wires at the bottom of the picture are the black and black w/orange stripe wires.

Here are some close ups:

I'll take a look through that website but on first glance it doesn't look to have any more info than my shop manual although I might have missed something.

Also, does anyone know what this is? Is it factory? I'm not sure where the other end of it is....

 

[brianj5600]

The plug in the last picture is the voltage regulator plug. It has been 3 or 4 years since I went through all that. I don't remember what all of those wires are. If someone does not help out before tomorrow I will be home and can look at my manual.

 

[2+2GT]

The plug in the last picture is the voltage regulator plug. It has been 3 or 4 years since I went through all that. I don't remember what all of those wires are. If someone does not help out before tomarrow I will be home and can look at my manual.

The eye next to the VR plug is a ground that gets screwed under one of the VR mounting screws.

 

[69gmachine]

From the looks of it this harness has been spliced, so you need to ring out each circuit to be sure it goes where it should. You should also plan on getting a new repro harness soon.

From the size and style of the terminals, the group that extend past the solenoid probably goes to the alternator. The white wire should be the FIELD, the black pair is GROUND and the dark wire would be the stator. But again, you really need to use a multi meter to ring out the harness and check it against the wiring diagram. What's missing is the large wire that brings power to the battery side of the start solenoid. This appears to be a harness for a Tach car.

At the solenoid the red/blue 90 degree boot goes to the I terminal, and the brown 90 degree boot goes to the S terminal. The black/yellow goes to the battery side of the solenoid. You need to find the other end of this wire and make sure it goes to the batt terminal of the alternator. The red wire with the large loop goes to the starter side of the solenoid. It's a prove out circuit. When you start the car it powers one of the lights in the dash to verify the bulb is working. I'm not familiar with the 67 cars, so I can't tell you what bulb it lights. Cars with the LOW FUEL light used a red wire like this.

With both a tach and a prove out circuit, the headlight harness appears to be from a highly optioned car. Do you know if this is the original wire harness?

 

[pyroman]

From the looks of it this harness has been spliced, so you need to ring out each circuit to be sure it goes where it should. You should also plan on getting a new repro harness soon.

From the size and style of the terminals, the group that extend past the solenoid probably goes to the alternator. The white wire should be the FIELD, the black pair is GROUND and the dark wire would be the stator. But again, you really need to use a multi meter to ring out the harness and check it against the wiring diagram. What's missing is the large wire that brings power to the battery side of the start solenoid. This appears to be a harness for a Tach car.

At the solenoid the red/blue 90 degree boot goes to the I terminal, and the brown 90 degree boot goes to the S terminal. The black/yellow goes to the battery side of the solenoid. You need to find the other end of this wire and make sure it goes to the batt terminal of the alternator. The red wire with the large loop goes to the starter side of the solenoid. It's a prove out circuit. When you start the car it powers one of the lights in the dash to verify the bulb is working. I'm not familiar with the 67 cars, so I can't tell you what bulb it lights. Cars with the LOW FUEL light used a red wire like this.

With both a tach and a prove out circuit, the headlight harness appears to be from a highly optioned car. Do you know if this is the original wire harness?

Lots of good info here thanks!

I do plan on rewiring the car entirely in the future but the current project has cost me alot so I need to let my money recuperate. I'm a little new to wiring so excuse my ignorance but what do you mean exactly by 'ring out'?

Since I'm adding in the 3G I shouldn't need those last wires that extend past the solenoid (if they go to the alternator) correct? As far as making sure that the wires connect to the alternator, does it matter since I'm no longer using the factory alternator?

I do believe I have the LOW FUEL light. Just a red lightbulb on the dash right? It's never worked however. Possibly just a burned out bulb? What else could be the issue?

The car itself is fairly highly optioned. It has the deluxe interior with the full console. However it does not have a tach which if you are correct would leave me to believe that it is not an original harness. Other than that I can't say whether it is or isn't, I've only had the car for 7 years.


In regards to the connection for the voltage regulator, does the ground with it need to be connected if I'm no longer using it?

Thanks again

 

[69gmachine]

I'm not real familiar with the 3G alternator, but all late model alternators have an internal regulator so you should only need to connect it to the battery. I'll let someone with 1st hand experience take over from here.

OK, now for electrical troubleshooting 101:

To "ring out" a wire harness assembly (WHA) means to check for continuity from end to end of each wire, and to verify there are no shorts either to ground or to other wires in the harness (in an aircraft it would also include checking for shorts to shield, but there are no shielded wires in a classic Mustang).

Using a multi meter, set the function to OHMS and the scale to the lowest setting. Touch one end of the test wire with the red lead and the other end with the black lead. It doesn't matter which end goes where for continuity. Obviously this test is best suited for when the harness is out of the car. If a wire has been spliced on to the end of a harness, the color may not follow the factory schematic so you may need to physically trace the wire run. Some meters have a setting that will buzz for continuity. The problem doing this is that even a high resistance will get a buzz. Using the ohmmeter function will give you an idea of the health of the wires. All the wires in the same harness of the same gauge and length should have very similar (and low) resistance readings of less than one ohm. If you get continuity but a high resistance reading you need to figure out why. This is most often due to corrosion at junctions (including switches), so you shouldn't have this problem on any single WHA. Make sure the terminals are clean and use dielectric grease to keep moisture out before re-assembly.

To test for shorts to ground the WHA should be installed. Disconnect the end that sources power from the fuse block or battery, but leave the other end connected to the next WHA or whatever device it connects to. Touch one of the leads to the wire under test and the other to the frame making sure you get to the metal surface for a good ground. If you have continuity then either there is a short or a switch is closed. You need the wiring diagram to determine where the switch is. If you find there is a switch, open it and test again. If you still have continuity there is a short to ground. If there is more than one WHA before the signal goes to ground, move to the next junction, disconnect and repeat the test. Common causes for a short to ground are a stuck/bad switch or a wire that has had the insulation cut and is rubbing against the metal frame.

To test for shorts to other wires in the harness just touch one lead (lets say the red one) to one wire and then touch the black lead to all the other wires one at a time. Move the red lead to another wire and repeat the procedure with the black lead touching all the others. Repeat until you have checked every wire. If you find continuity, check against the schematic. If they are not connected somewhere on the schematic, you have to find the short and fix it. The best way is to buy a new harness.

As you can see, without a good wiring diagram you're not going anywhere. These old cars are incredibly simple, and with the right tools they can be repaired by anyone almost anywhere.

 

[65FBE2]

Looks to me like the fist pic has the wires that go to the starer solenoid. They will all need to be hooked up. The bottom bunch by the bumper, you need to find the one that goes to the battery. I think it is the one that has a ring at the end but is only a single wire but not sure. Connect this wire to your 1-wire alternator. Just fold the rest of the wires back and tape them over so they can't short. You can leave the factory voltage reg installed and hook the plug up so it looks factory. It will not function and has no power going to it if you did this correctly.

I just did this and you can not tell its not a factory set up. Leave the reg installed as it just looks cleaner in my opinion

 

[pyroman]

I'm not real familiar with the 3G alternator, but all late model alternators have an internal regulator so you should only need to connect it to the battery. I'll let someone with 1st hand experience take over from here.

OK, now for electrical troubleshooting 101:

To "ring out" a wire harness assembly (WHA) means to check for continuity from end to end of each wire, and to verify there are no shorts either to ground or to other wires in the harness (in an aircraft it would also include checking for shorts to shield, but there are no shielded wires in a classic Mustang).

Using a multi meter, set the function to OHMS and the scale to the lowest setting. Touch one end of the test wire with the red lead and the other end with the black lead. It doesn't matter which end goes where for continuity. Obviously this test is best suited for when the harness is out of the car. If a wire has been spliced on to the end of a harness, the color may not follow the factory schematic so you may need to physically trace the wire run. Some meters have a setting that will buzz for continuity. The problem doing this is that even a high resistance will get a buzz. Using the ohmmeter function will give you an idea of the health of the wires. All the wires in the same harness of the same gauge and length should have very similar (and low) resistance readings of less than one ohm. If you get continuity but a high resistance reading you need to figure out why. This is most often due to corrosion at junctions (including switches), so you shouldn't have this problem on any single WHA. Make sure the terminals are clean and use dielectric grease to keep moisture out before re-assembly.

To test for shorts to ground the WHA should be installed. Disconnect the end that sources power from the fuse block or battery, but leave the other end connected to the next WHA or whatever device it connects to. Touch one of the leads to the wire under test and the other to the frame making sure you get to the metal surface for a good ground. If you have continuity then either there is a short or a switch is closed. You need the wiring diagram to determine where the switch is. If you find there is a switch, open it and test again. If you still have continuity there is a short to ground. If there is more than one WHA before the signal goes to ground, move to the next junction, disconnect and repeat the test. Common causes for a short to ground are a stuck/bad switch or a wire that has had the insulation cut and is rubbing against the metal frame.

To test for shorts to other wires in the harness just touch one lead (lets say the red one) to one wire and then touch the black lead to all the other wires one at a time. Move the red lead to another wire and repeat the procedure with the black lead touching all the others. Repeat until you have checked every wire. If you find continuity, check against the schematic. If they are not connected somewhere on the schematic, you have to find the short and fix it. The best way is to buy a new harness.

As you can see, without a good wiring diagram you're not going anywhere. These old cars are incredibly simple, and with the right tools they can be repaired by anyone almost anywhere.

Lots of good info here, thanks . I will definately use this when it comes to start rewiring the car.

Looks to me like the fist pic has the wires that go to the starer solenoid. They will all need to be hooked up. The bottom bunch by the bumper, you need to find the one that goes to the battery. I think it is the one that has a ring at the end but is only a single wire but not sure. Connect this wire to your 1-wire alternator. Just fold the rest of the wires back and tape them over so they can't short. You can leave the factory voltage reg installed and hook the plug up so it looks factory. It will not function and has no power going to it if you did this correctly.

I just did this and you can not tell its not a factory set up. Leave the reg installed as it just looks cleaner in my opinion

Why would I need to connect this wire to the alternator? And why would one go to the battery, it seems to extend well past the stock location of the battery.

I'm not really concerned about having a factory set up so I'll just toss the regulator...if I can find it that is, haha. I'm not sure what I did with it...

 

[65FBE2]

Only if your going to use that harness, If you look at a factory wiring diagram you will see that wire connects to the battery. You have to have one wire from the alternator connect to the battery and it might as well be the one you have already in the harness. As far as the old regulator goes, doesn't matter what you do, reconnect it or throw it over the fence. I just don't like the looks of a wire plug hanging around the front of the car without anything connected to it

My car is a 65 and on it the wire that needs to be connected to the alternator is black 10 ga, with a white stripe, You will have to check a wiring diagram for your year. That wire goes all over the car but as long as it connects to the battery, it will work for a 1-wire setup

 

[pyroman]

General question here about the grounds. I have a block to frame ground and a block to firewall ground. I'm relocating the battery to the trunk and will MSD, electric fan, 3G goodies like I mentioned earlier. Should I upgrade these grounds? I'm thinking a 4 AWG cable for my block to frame ground (replacing the ground strap) and getting a new reproduction block to firewall ground. The old one is ratty. Are there anyones I missing? Should I add anymore?

 

[69gmachine]

As you mentioned, the firewall ground wire is more for looks than anything else as you only need one ground strap to the block. If your ground strap to the frame is nice and wide leave it there. I use a 1" wide braided stainless steel strap to the frame for both a DC and RF ground. A large surface area will help to conduct RF away from the engine, minimizing radio interference from your ignition.

Unless you're designing to survive a Mil-Spec lightning strike, you already have adequate grounds to the block. Use a short negative cable to the frame and you're done.