Intermittent electrical issue

[JDuvall]

I plan to test this evening, we had a cold snap come through and I had to watch the Chiefs play, so I was a little preoccupied.

 

[JDuvall]

Sorry for a long delay, had to travel for work.
So my starter is dead, shorted to ground. This explains the dead battery and not starting. May explain the some of the voltage issues as well. More updates and pic to come.

 

[JDuvall]

New starter in and still having issues. Going to recheck all connection and try again in the morning.

 

[JDuvall]

Well I believe I found my issue. Only time will tell. I put Everything back together and it would only buzz the starter solenoid. I jumped out the solenoid and the motor cranked over. So I went and got a new starter solenoid cleaned the grounds and when I went to put the wires back on the fusible link terminal broke off.
I have replaced the fusible link with an actual fuse and holder. Everything starts ups and runs now. I have my fingers crossed but so far so good.

 

[Cleveland Crush]

Yep Duvall, I believe you found the gremlin. Way to go!

 

[mrgmhale]

Well I believe I found my issue. Only time will tell. I put Everything back together and it would only buzz the starter solenoid. I jumped out the solenoid and the motor cranked over. So I went and got a new starter solenoid cleaned the grounds and when I went to put the wires back on the fusible link terminal broke off.
I have replaced the fusible link with an actual fuse and holder. Everything starts ups and runs now. I have my fingers crossed but so far so good.

Many thanks for taking the time to post a follow-up. And for taking the photo of the Fusible Link that had its terminal end break off. Whenever I read books on vehicle wiring, when it comes to diagnosing open circuits (and presumably intermittent open circuits) the author typically includes a comment about checking fuses and Fusible Links. But, in my 52 some odd years of working on and tinkering with these First Generation Mustangs, I only rarely ever saw a problem with them. And those few problems involved they having become overloaded and burning out, although there is no doubt the terminals could be poorly connected during original construction, like what you found.

So, your photo will burn brightly in the back of my mind when it comes to open circuits, especially if it is an intermittent open circuit. Good job finally finding that. I sincerely hope that is the only cause if your electrical maladies.

 

[JDuvall]

Many thanks for taking the time to post a follow-up. And for taking the photo of the Fusible Link that had its terminal end break off. Whenever I read books on vehicle wiring, when it comes to diagnosing open circuits (and presumably intermittent open circuits) the author typically includes a comment about checking fuses and Fusible Links. But, in my 52 some odd years of working on and tinkering with these First Generation Mustangs, I only rarely ever saw a problem with them. And those few problems involved they having become overloaded and burning out, although there is no doubt the terminals could be poorly connected during original construction, like what you found.

So, your photo will burn brightly in the back of my mind when it comes to open circuits, especially if it is an intermittent open circuit. Good job finally finding that. I sincerely hope that is the only cause if your electrical maladies.

Thank you for the kind words. I hope is helps others as well. I know it is sometimes hard to find information on things like fuseable links and 90% of the time it is working or it is blown. Rarely is it broken with intermittent contact.

 

[JDuvall]

The gremlins struck again. After a month of no issues, the loss of all power came back. As I am wanting this car to be a daily driver , I can’t have theses issue keep coming up. I have to face the facts that I am dealing with 50 year old plastic, wire and technology. Time to upgrade!

If anyone has an old dash harness or the headlight switch connector along with the instrument cluster connect they wouldn’t mind getting rid of please let me know. I am going to try and keep my old harness uncut.
So good by my free time for a few days.

 

[Steve McMahan]

Sorry to hear. Ok, back to basics, unfortunately. The wire in question, 37, starts at the starter solenoid, and without a break, goes to the c-211 or the fuse block. From there, it branches out to the headlight switch, etc; all areas you have said have no power with this gremlin strikes. So, the only logical place the intermittent issue can occur in are, 1 that one piece wire, or 2 that fuse block. I agree with Midlife that a break in that continuous wire is unlikely, but not impossible.

I think you have to pull that c-211 connector apart and check the connectors for #37 on each side to see if the wire to or post the connector look bad. It might be the pins themself. If the wires look ok, I would clean it thoroughly and see what that does. It’s got to be one or the other.

 

[JDuvall]

Sorry for not updating, found the issue. The new starter is shorted to ground. It is causing the voltage to go to zero. That with an ignition switch not align right caused this issue. I am replacing the oem style starter with a high torque low amp starter. I am also going to rewire the fuse box to put the fuses in a more accessible place.

 

[JDuvall]

Sorry to hear. Ok, back to basics, unfortunately. The wire in question, 37, starts at the starter solenoid, and without a break, goes to the c-211 or the fuse block. From there, it branches out to the headlight switch, etc; all areas you have said have no power with this gremlin strikes. So, the only logical place the intermittent issue can occur in are, 1 that one piece wire, or 2 that fuse block. I agree with Midlife that a break in that continuous wire is unlikely, but not impossible.

I think you have to pull that c-211 connector apart and check the connectors for #37 on each side to see if the wire to or post the connector look bad. It might be the pins themself. If the wires look ok, I would clean it thoroughly and see what that does. It’s got to be one or the other.

View attachment 75346

I also forgot to say thank you Steve, the prints help a lot! I also did the exact thing you said to do. I pulled the c-211 apart and spread the male connector out to make better contact. I then did a continuity test from the battery to all exposed 37 points (head light sw, ignition sw, c-211 and the relay panel). It all checked out fine. I then put my voltage meter on the 37 wire to see what happens when I try to start the car. That when I saw it drop Voltage to zero. I disconnected the starter from the solenoid and checked again, had 12v. I tried a different battery and with a booster to make sure I didn’t have a week battery.

Again thank you Steve and everyone else that has been helping out. It is greatly appreciated!

 

[Steve McMahan]

Sir, it was my pleasure if anything I did helped. I can’t pay it forward enough for all the help I’ve received from these guys. I mean, look at the facts: me with my very limited skills, did an 87 TBird EFI swap into my 73, built a wire harness that worked (no codes on the computer), and all of it happened because when I got stuck, folks who didn’t owe me anything, stopped what they were doing to help me. And, when I needed a weird part, sure enough, someone had one. I don’t know what else to say, but it’s these guys who deserve the thanks.

 

[JDuvall]

Some updates, on my electrical issues. I have changed out the oem style starter and went with a high torque starter with a solenoid on the starter. Added a positive bus bar (red box) to make hooking power up easier. Went with 2 gauge wire for the starter and ground. New dry cell optima red top battery along with a new 6 fused relay box.
I am still working on the inside wiring, but for now she fires right up and no electric issues as of now.

 

[bdennis]

Per an earlier post. Where does the negative heavy duty wire go from the battery? Does it go direct to the block or does it go from the battery to the body and then to the block? I had issues and found that the black / or negative only went from the battery to the block and the rest of the car was getting the ground via other components and causing all sorts of issues. The black heavy duty wire should go from the negative of the battery to the body and then to the block.

 

[JDuvall]

Per an earlier post. Where does the negative heavy duty wire go from the battery? Does it go direct to the block or does it go from the battery to the body and then to the block? I had issues and found that the black / or negative only went from the battery to the block and the rest of the car was getting the ground via other components and causing all sorts of issues. The black heavy duty wire should go from the negative of the battery to the body and then to the block.

Current it goes to the block. I am going to change it soon when I get more ground cables. I want to go to body, engine block and alternator.

 

[mrgmhale]

I have a video showing where the battery cables go on a 69/70 Mustang. This is largely unchanged with 71-73 Mustangs. The shots were done with an iPhone, and the tight quarters made it hard to dhow as much detail as I would have liked.

https://www.youtube.com/watch?v=0GC6m_OqzLs

In the attached PDF for the Mustang Starting system there is a drawing you can reference on Page 2. It is not as detailed as I would have liked, but if you zoom in on the drawing you will see where the battery cables go.

There is a snippet from the 1971 Mustang wiring schematic, on page 4, that shows the routing of the battery cables. It is similar to the 1969 routing mentioned in the preceding paragraph.

The negative cable itself has a negative terminal lug for the battery post, an interim negative cable eyelet connector that mounts to the inner fender at the voltage regulator, using a voltage regulator mounting screw, and the far end has another eyelet connector help in place with a
bolt going into the driver side, front cylinder head in a threaded boss made for said connection. A view of the battery cable, with its interim connector that is mounted using a voltage regulator screw shown. Attached is another file with cable routing details.

 

[Mach I Pony]

Thank you MRGMHALE I'm working on my ignition system and this exactly what I was looking for. Got some wires cross and went crazy and disconnecting everything ( which didn't help at all) two hours later and she's back running again

 

[mrgmhale]

Thank you MRGMHALE I'm working on my ignition system and this exactly what I was looking for. Got some wires cross and went crazy and disconnecting everything ( which didn't help at all) two hours later and she's back running again

I am happy to help out fellow enthusiasts wherever I can. Lots of other members do the same. Somehow or another we all manage to get some good into out there.

If you need more detailed photos or video than what I show for our 69 Shelby let me know. I have finally been able to take our ponies out of the Winter Hibernation (Snow Country, Rochester, NY).

 

[JDuvall]

My glovebox electrical panel is ready to install. The three fuse block are left to right, battery powered, lights switch powered, ignition switch powered.
The leds in center of the blocks light up if fuse is blown.
Will update once installed .

 

[JDuvall]

My glovebox electrical panel is ready to install. The three fuse block are left to right, battery powered, lights switch powered, ignition switch powered.
The leds in center of the blocks light up if fuse is blown.
Will update once installed .