Mini wire fire

[Aviodont]

I have an 83 K5 for the last 9 years. I don’t use it often and it is parked in the driveway. To keep the battery from discharging, I disconnect both cables from the terminals and reconnect them every few months to start her up.

the last time I began this procedure, as soon as I connected the last battery cable, smoke started appearing from something on the firewall. I immediately disconnected the cables to prevent a fire. The keys were not in the ignition at any time and the headlights were not on.

after getting a fire extinguisher out of the house, I repeated the procedure and this time there was no fire/smoke. But the engine would not crank at all once the key was turned. No clicks.

I want to figure out what the problem may be. Or maybe I should say my teenage boys are also keenly wanting to figure out what the problem is.

Can someone tell me how to attach pictures to assist?

 

[nvrenuf]

You cannot attach pics with a free membership. You will need to put the pics on the net somewhere that’ll host them a as md once you have more than 5 posts you can link them.

A paid membership will allow you to attach pics or host them in the sight gallery right away.

The site is set up like this to prevent bots and knuckleheads from posting stuff that doesn’t belong here.

 

[Fordum]

Two thoughts: One, hooking the cables up backward can cause those symptoms, Second, sitting up for a long time is an open invitation for rodent action.
Look around where you saw the smoke coming from, looking for rodent droppings, and small pieces of wire or insulation. Also use your nose. Rodents have a very distinctive smell. If you have ever smelled a nest, you will remember.

J,

 

[rampage]

Two thoughts: One, hooking the cables up backward can cause those symptoms, Second, sitting up for a long time is an open invitation for rodent action.
Look around where you saw the smoke coming from, looking for rodent droppings, and small pieces of wire or insulation. Also use your nose. Rodents have a very distinctive smell. If you have ever smelled a nest, you will remember.

J,

^^^ X2
You probably blew a fuse or fusible link. Definitely a short that you’ll have to track down … or actually, this sounds like a good job for your boys.

 

[Wes Harden]

Something is shorted to ground. to melt wires at the firewall chances are it was at the junction block. this powers head lights, alternator, horn, it also supplies power to the ignition switch and the courtesy circuit.
The power to the junction block is connected at the starter solenoid, same spot as battery. The diagram I am attaching, and will send you, middle top shows 2A and 2H. Both of these are power feed to the truck. One or both melted and separated when the short occurred. The fuse links will need to be repaired. Inspect the loom from the firewall along the intake to alternator. Rodents love to chew plastic and insulation.
Look for damage to the wiring, check that no wires are touching the exhaust manifold near the starter.
After the fuse links have been inspected and if needed repaired, connect the positive cable to battery, use a test light between the battery negative and the negative cable. If the light is on you have a draw/short. 1st I would disconnect the batt + wire to alternator. If light goes out the alt has internal short. Next would be the horn relay. If there is still a draw things get more in depth. take a look and let us know what you see and find.


Welcome to the Board @Aviodont

 

[Aviodont]

Something is shorted to ground. to melt wires at the firewall chances are it was at the junction block. this powers head lights, alternator, horn, it also supplies power to the ignition switch and the courtesy circuit.
The power to the junction block is connected at the starter solenoid, same spot as battery. The diagram I am attaching, and will send you, middle top shows 2A and 2H. Both of these are power feed to the truck. One or both melted and separated when the short occurred. The fuse links will need to be repaired. Inspect the loom from the firewall along the intake to alternator. Rodents love to chew plastic and insulation.
Look for damage to the wiring, check that no wires are touching the exhaust manifold near the starter.
After the fuse links have been inspected and if needed repaired, connect the positive cable to battery, use a test light between the battery negative and the negative cable. If the light is on you have a draw/short. 1st I would disconnect the batt + wire to alternator. If light goes out the alt has internal short. Next would be the horn relay. If there is still a draw things get more in depth. take a look and let us know what you see and find.


Welcome to the Board @Aviodont

View attachment 423657

Thanks for the diagram Wes. The smoke was definitely coming from the junction block.

There is a wire that has exposed wiring (either burned off or chewed) right at the connection to the junction block. It is the middle wire (lighter shade of red) on the drivers side.

For reference, the passenger side of the block has one red wire. The drivers side has three. Top is black, middle is the light red that has the exposed wiring, and the bottom is red.

 

[Aviodont]

Something is shorted to ground. to melt wires at the firewall chances are it was at the junction block. this powers head lights, alternator, horn, it also supplies power to the ignition switch and the courtesy circuit.
The power to the junction block is connected at the starter solenoid, same spot as battery. The diagram I am attaching, and will send you, middle top shows 2A and 2H. Both of these are power feed to the truck. One or both melted and separated when the short occurred. The fuse links will need to be repaired. Inspect the loom from the firewall along the intake to alternator. Rodents love to chew plastic and insulation.
Look for damage to the wiring, check that no wires are touching the exhaust manifold near the starter.
After the fuse links have been inspected and if needed repaired, connect the positive cable to battery, use a test light between the battery negative and the negative cable. If the light is on you have a draw/short. 1st I would disconnect the batt + wire to alternator. If light goes out the alt has internal short. Next would be the horn relay. If there is still a draw things get more in depth. take a look and let us know what you see and find.


Welcome to the Board @Aviodont

View attachment 423657

Wes,

thanks so much for the help. I am out now, but earlier, I did the following.

With no key in/lights on, I connected positive cable to battery. Put voltmeter between negative battery post and negative battery cable (kinda in-line). It reads 12.5V. So to me that means a short.

Next, I connected the voltmeter from negative battery post to the red wire of the two pin connector on the side of the alternator (other wire is either black or dark brown) and got 12.5V.

When I follow the wire that is black at the junction block, it becomes green within 6 inches and later disappears through the firewall near the brake booster.

 

[BoondocK5]

You'll need to figure out what that red wire goes to,and repair it. Like Wes said, check and repair any fuseable links that went to wire heaven. I've seen 6 inch pieces of 10gauge fuseable link at NAPA, on the wiring/electrical shelf, in Individual packages. If you don't want to buy a spool. Guys like me buy the spool, if your new the wiring game, definitely, buy the individual.

 

[Aviodont]

Just for clarification, in post #7, when I typed “ no key in/lights on “, I intended to say “no key in and no lights on”

 

[Fordum]

I want to make sure, first of all, that you are familiar with the concept of a fusable link. Its a piece of wire between the battery and some heavier wire. It usually is in a place where there is nothing too flammable, and has insulation that will not burn. It is designed to melt and open the circuit before the downstream wire does. It has to be the correct gauge for the load it expects to see and the circuit it is protecting.
It acts like, and basically is, a fuse. Its just not in a cute package. The main problem we see with them, is that people think they are just a piece of wire and replace them with whatever size wire they have laying around. If they put on a larger wire, then the fire occurs somewhere else.
Also, that insulation not only does not support fire, but it sometimes does not melt much. This causes problems because the wire inside may be burned up, but it does not look like it from the outside. A gentle pull on the wire will show the problem, because it will stretch or pull in two.

Second of all, the way you tested for a short, is not much good. Putting a voltmeter between the negative (or positive) battery terminal and it's cable only reveals if there is any kind of load. Not how much it is. Given the very high resistance of a voltmeter, one small dash light would result in full voltage on the meter.
Instead, you need to measure how much current is being drawn. DO NOT do that with the meter set on amps!
Most meters limit out at about 20 amps, and a short in the wiring could draw several hundred. Plus, if the meter could take it, you would get the same amount of smoke as you would hooking the terminal back up.

Instead, you need something in place of the meter that will show current draw, but at the same time limit how much current it allows through.
A light bulb is good. You can use a test light in place of the meter inline with the cable for small loads. You would do that if you had something draining your battery over time. A very dim light would mean a tiny load, and a bright one a big load.
However you are big game hunting here. You are looking for a major load. One of the best things I have found is an old headlight bulb. One of the old sealed beams from the junkyard, or "borrowed" from the truck its self is good.
A dim light means not much of a short if any at all.
A nice bright light means a big short, and supplies you with a nice light to hunt it by. Disconnect things until it goes out or gets dim.

J.

 

[Aviodont]

I think I found a workaround for the photo thing. I made a YouTube video.