Electrical Issue. Wire burn

[CTan]

Fusible links 86' K10

Thanks in advance for all your help.

I have a 86' K10 that has had the 305 swapped for a crate 350 HO.

I killed my battery today by leaving the headlights on this morning. I went back out 4 hours later and it just clicked when I went to start the truck. I got a buddy to jump me and let the truck idle for about 5 min after jumping. I drove about 2 blocks and smelt burning wiring. When I pulled over the red wire that connects to the firewall junction block had burnt all the insulation off and the wire broke. This is the red wire that is a single wire on the junction block then splits into two wires , one to the alternator and one to the fuse block. Every time I bridge the wire it over heats the new wire as its drawing too much current. With it open I have no voltage to anything inside the truck. This wire normally has 12 V as attested by the burn on the tips of my fingers when I was connecting a jumper wire.

Here's what I have tried so far. I pulled all the fuses that weren't needed and no change.

My alternator is putting out 14.7 V at idle and 16.2 V at 3000 rpms.

With all wires disconnected from terminal block, I have a dead short on the small terminal of the starter solenoid with the red wire. Is this normal and can the solenoid short and still work?

I just want to make sure its the solenoid and not the neutral safety switch or ignition switch before I pull the starter. See pic below. Arrow points to the wire that burnt on my truck and that entire single section of wire burnt. This isn't a pic from my truck but from another.

 

[dhamp]

Have you tried pulling the wire away from the firewall to make sure it's not grounding out there?

 

[CTan]

Yea, the wire is away from the firewall. I found out that I have almost an open at the firewall terminal (150K ohms) but with the key on I have a dead short. Can an ignition switch go bad, as in short, and still work?

 

[oneluckypops]

The wire your showing in your picture is a fusible link. Best bet would be to Temporarly delete the link with a circuit breaker, then use an old style amp meter and run it down the wire to find the short. If you go to www.realfixesrealfast.com he has a video of the diagnostic procedure to find shorted wires, he is very easy to understand and is IMO a pretty good tech.

 

[Affende]

I just had this same problem with my 83 c15 w/ 250 when trying to move it around the house. Dead duck. I spliced in a section of 10awg to get it moved to the garage so I could fix other issues (improperly mounted starter, chaffed and worn battery cables, misc electrical connections).

No idea what the proper fix is (I put effort into avoiding electrical work). No idea why it shorted in the first place. I'll be following this thread to see what the knowledgable members have to say.

 

[chengny]

Jumping a fusible link to get the truck in the garage? And with a 10 gauge wire no less.

What was the old saying - "No guts, no glory"?

Dude, you must be living right. It is generally considered to be really bad practice to disable a circuit's overcurrent protection. Don't get me wrong, I'm not preaching. I may have done something similar in the past.

You didn't place yourself in any harm, but you're lucky you still have a functional wiring harness. An in-line fuse or a tiny (like 22 gauge) wire would have been a better choice but that is moot now. The truck is in the garage, and you can locate the fault that caused the over-current situation - if one ever existed.

It is not unheard of that a fusible link will fail mechanically from age, vibration, someone stepping on the connecting wires, sabotage, etc. The fact that you didn't burn up any part of your harness should give you some degree of hope that maybe the link failed for reasons other than over-current.

I would buy an in-line fuse holder and splice it in where the link was. Insert a low amp fuse (10 amps maybe) and go about your repairs.

If the 10 amp fuse hangs in there, leave it be. If it blows go to a 15 amp fuse and see if that is thick enough to carry the circuit load. You can do this (keep upping the amperage), until you hit a fuse that is rated high enough to carry the load.

If there is an actual ground fault/short circuit, at some point you will have to accept that fact and begin the process of locating it. Don't bother to go any higher than a 30 amp fuse. If that isn't sufficient, you surely do have a problem - admit defeat.

 

[Affende]

Jumping a fusible link to get the truck in the garage? And with a 10 gauge wire no less.

What was the old saying - "No guts, no glory"?

Dude, you must be living right. It is generally considered to be really bad practice to disable a circuit's overcurrent protection. Don't get me wrong, I'm not preaching. I may have done something similar in the past.

You didn't place yourself in any harm, but you're lucky you still have a functional wiring harness. An in-line fuse or a tiny (like 22 gauge) wire would have been a better choice but that is moot now. The truck is in the garage, and you can locate the fault that caused the over-current situation - if one ever existed.

It is not unheard of that a fusible link will fail mechanically from age, vibration, someone stepping on the connecting wires, sabotage, etc. The fact that you didn't burn up any part of your harness should give you some degree of hope that maybe the link failed for reasons other than over-current.

I would buy an in-line fuse holder and splice it in where the link was. Insert a low amp fuse (10 amps maybe) and go about your repairs.

If the 10 amp fuse hangs in there, leave it be. If it blows go to a 15 amp fuse and see if that is thick enough to carry the circuit load. You can do this (keep upping the amperage), until you hit a fuse that is rated high enough to carry the load.

If there is an actual ground fault/short circuit, at some point you will have to accept that fact and begin the process of locating it. Don't bother to go any higher than a 30 amp fuse. If that isn't sufficient, you surely do have a problem - admit defeat.

it was a short term fix, apparently incorrect, but it worked for its intended purpose to get the truck out of the middle of the yard (just because i live in TN doesnt mean i **** a junk yard in front of the house ).

This was my great grandfathers truck, bought it new in 83, got sold in the late 80s, grandfather bought it back in the early 90s, uncle destroyed it in the early 2000s, mom got it in 04 and we used it on the farm till 2010 ... now i have it and want to do a restoration.

It lived the life of a company truck (great grandfather and grandfather were in lumber), the neglected daily beater (wrecked, no maintenance) and farm truck (field rats, trash, never washed or covered). The wiring harness has 31 years of splicing, cutting, burning, melting, more splicing, more cutting etc.

To do it right, i am already looking for a new wiring harness for a complete frame off. I want my son to help and drive this truck when he is old enough so a full redo is all that will work .... and im picky as hell when i have the time.

thanks for the info, ill get a fuse and wire it in so salvage what little is left until the tear down starts.