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So, a few months ago, I was doing a tune up on my 1968 Chevy Chevelle malibu with a 307 small block. Changed the spark plugs, wires, coil, rotor and cap and forgot to put the coil wire back on. I got in the car and tried cranking it and the engine never would turn over due to the coil wire being disconnected. I got out found the coil wire was disconnected reconnected it got back in and tried starting it. it turned over and ran for 2 seconds then BOOOM the fuse link popped, and white smoke came out of the fuse link wire. it killed battery and the car no longer cranked. I replaced the wire, fuse link and the battery and tried starting the car but upon inserting the key into the ignition. No lights, buzz, crank or anything. Now the only thing that happens it when I connect the battery the headlights turn on and stay on unless I unhook the battery. what did I manage to screw up this time Lol
 

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I had my fusible link go in one of my cars a ways back. I called M&H wiring to get the 22 gauge link and they said many times when a fusable link goes it destroys the wire connection within the bulkhead connector. It is probably worth it to separate the harness and physically look and ohm out the connection. In my case everything was ok but you need to understand a fusible link allows much more current to pass through the circuit before opening then a fuse would so it is possible that the bulkhead connector or the wire itself is burned up or has very high resistance.
 

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Which fusible link did you replace?
Did you check all your fuses under the dash and were any blown out?
With the key on are you seeing power to all fuses? Knowing where you have power will help isolate the section of the circuit we need to be looking at.

You said with the coil disconnected it would not turn over. Did you mean it would turn over but not start?

Headlights staying on is sort of leading me to think you have a short that is shorting out to the headlight circuit. I'm not sure, just spit balling right now. Can you reach the headlight switch and disconnect the wires? I want to eliminate the switch as the source of the headlights staying on. If they stay on with the switch disconnected, we'll have to find out why.

I'm thinking the headlights staying on is the big clue. I just haven't put the pieces together yet.

Do you have a test light and ohm meter?
 

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Considering the headlight circuit is only indirectly connected to/powered off of the main fusible link feeding the cabin, you have other issues. It's time to look in places that you tampered with.
 

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it is possible other wires were damaged and melted in the harness between the firewall block to the voltage regulator and / or going the other way to the distributor and starter area...
you will want to check both legs of this harness and the connectors at the firewall block assembly...
 

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it is possible other wires were damaged and melted in the harness between the firewall block to the voltage regulator and / or going the other way to the distributor and starter area...
you will want to check both legs of this harness and the connectors at the firewall block assembly...
Yup, and one is contacting the headlight circuit. Others feeding the items not working
I had my fusible link go in one of my cars a ways back. I called M&H wiring to get the 22 gauge link and they said many times when a fusable link goes it destroys the wire connection within the bulkhead connector. It is probably worth it to separate the harness and physically look and ohm out the connection. In my case everything was ok but you need to understand a fusible link allows much more current to pass through the circuit before opening then a fuse would so it is possible that the bulkhead connector or the wire itself is burned up or has very high resistance.
It sounds like no power is entering past the bulkhead connector into the cab. The connections in the bulkhead area can be a high resistance area where heat would build first. One highly suspect spot is in the bulkhead connector, and the wire harness forward to the 4 way splice as this contains both the main feed and the headlight circuit.

Knowing where he has power in the fuse box would help narrow down the search. I don't think he will find any power there. That would put me searching from the bulkhead connector forward to start. I wanted to disconnect the headlight switch to eliminate that as a cause, but I doubt he will find power there.
 

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Yup, and one is contacting the headlight circuit. Others feeding the items not working


It sounds like no power is entering past the bulkhead connector into the cab. The connections in the bulkhead area can be a high resistance area where heat would build first. One highly suspect spot is in the bulkhead connector, and the wire harness forward to the 4 way splice as this contains both the main feed and the headlight circuit.

Knowing where he has power in the fuse box would help narrow down the search. I don't think he will find any power there. That would put me searching from the bulkhead connector forward to start. I wanted to disconnect the headlight switch to eliminate that as a cause, but I doubt he will find power there.
Al I know when I unwrapped my original 68 harness I was actually surprised to see how messy the 4 point solder connection was. I don’t have my AIM out but I believe it was 4 heavy 10 or 12 gauge wires soldered together and either electrical tape or harness wrap protecting it from a short condition. I could see heat from a short easily unsoldering that connection.GM should have used a better connection type or connector for that splice.
 

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Al I know when I unwrapped my original 68 harness I was actually surprised to see how messy the 4 point solder connection was. I don’t have my AIM out but I believe it was 4 heavy 10 or 12 gauge wires soldered together and either electrical tape or harness wrap protecting it from a short condition. I could see heat from a short easily unsoldering that connection.GM should have used a better connection type or connector for that splice.
The 4 way splice was not pretty. I think it was used because it was pretty cheap but did the job. They could have ran all these wires to the horn relay buss bar and achieved the same goal.

Automotive tire Motor vehicle Automotive exterior Bumper Fish
 

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Lonewolf, Have you looked for any signs of burned wires? Did you have a burning smell in the cab when this occurred?

I think you should pull the bulkhead connector under the brake booster. This will tell us if we should suspect the forward light harness or from the bulkhead connector through the dash harness. Disconnect the battery first.

The bolt is held captive in the carrier so it won't come out no matter how much you spin it. The carrier holds light harness and engine harness in place. As you remove the bolt, wiggle and pull out on the harness connectors. Once loose, connect the battery and see if the headlights come on. If they do we know the issue is in the forward light harness. The big red wire will be making a connection with the Tan wire. You can order a new forward light harness or repair the old.

No headlights tells us our issue is from the bulkhead connector back under the dash.

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The 4 way splice was not pretty. I think it was used because it was pretty cheap but did the job. They could have ran all these wires to the horn relay buss bar and achieved the same goal.

View attachment 730452
Nice thing was after they put on the wrap around connector to hold the wires together, they then soldered it.

This was the underhood splice off of a 67 Chevelle I worked on a few years back. The one leg went to the battery, another leg to the alternator output, another leg to the external voltage regulator, and the 4th leg to the horn relay buss.



Jim
 

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Now the only thing that happens it when I connect the battery the headlights turn on and stay on unless I unhook the battery. what did I manage to screw up this time Lol
Do you possibly have headlight relays on the car ?.

If so maybe the trigger wire for the relay melted to the feed wire when the short occurred to smoke the fusible link. I remember a car from years ago that a wire shorted in the harness and had to undo the wrapping and found more than one spot that the melted wire cut into and through into other wires creating unwanted connections and strange issues.

Jim
 

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Nice thing was after they put on the wrap around connector to hold the wires together, they then soldered it.

This was the underhood splice off of a 67 Chevelle I worked on a few years back. The one leg went to the battery, another leg to the alternator output, another leg to the external voltage regulator, and the 4th leg to the horn relay buss.



Jim
Jim I kept my harness somewhere in my basement. My 68 was like yours but I don't believe it had a metal wrap and was only solder. What was the insulation on that connection? In my case it was just tape and I believe that splice just sits on top of the metal inner fender. Not that yours is a great type of connection but that is better then mine. I inadvertently shorted out the connector to my amp gauge (heavy gauge feed) to my dash frame when I changed my tach and it blew my fusible link. Yes it happened after I connected the battery and I didn't work on it with the battery connected in case anyone was wondering :unsure: . I will dig though my stuff in the basement and find my old harness and post later.

EDIT: I only have my old cluster harness and threw out my engine harness and will assume mine was like yours. Still curious if your insulation was just harness wrap.
 
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