smoking wiring harness

after putting body back on i wired up what i needed to start engine, had everything labled but a couple faded on me and couldent read. thru process of elimination i got it, i thought, right. the engine started,good spark but i thought the coil was getting too hot, especially if the key was on but not running. today i started it put it in gear and drove down the drive. it died, thought was a gas prob. left key on and walked back to get gas, brown smoke everywhere harness toast! except the lighting & sending units that werent hooked up. thoroghly disgusted, where do i start? i dont know if the harness was just bad,dryrot, or if i had a connection wrong. any help is greatly appreciated. thanks

 

Sounds like you have a short somewhere. Does this wiring harness have fuses? If so you could pull them all out and put them back in one at a time to isolate the offending circuit.

 

Find the wire that melted. Just go to the location where the harness looks damaged, take the tape off and start carefully pulling apart the wires. Some wires may be melted to each other, but there will likely be one wire that got really hot. It should be obvious - the copper will be exposed and it will look different (oxidized, and all the strands coming apart) from the other wires.

I'd then simply repair everything. Cut out the damaged wire and replace it. Follow the melted wire back to its source.

In order to melt a wire, you must have a direct short to ground. You have to find that short. Up to you whether you fix the harness before you find the short or after you repair the harness. If the cause of the short is not obvious (ie a pinched wire, connector contacting the body, etc.) then you'll have to trace out the circuit to see where it is shorted. A test light or a multimeter is good for this.

How much do you know about electricity? You may need to educate yourself some if you don't understand what's happening.

 

well, i was an electrician before i was a boilermaker, thats not saying much though, forgot most of the theory, black hot, white neutral, green ground, bla bla. i think im gonna get couple rolls of wire, start with the diagram and replace each wire one by one. im thinking some insulation came of and grounded to the body somewhere.

 

If you leave the key in the on position and the points are closed it will heat up the oil in the coil and smoke it...not that I would know from first experience !!!

 

In the automotive world red (or other color) is hot and black is ground.

 

Regarding color, DOug is correct that black is (almost) always ground and red is a power lead, typically.

There are comparatively few ground wires, and they are usually short. The body and frame is used as the ground conductor for most purposes.

The manufacturers use colored wires so that the different circuits can be identified. If you look at the wiring diagram, you'll see the colors listed. Often they are abbreviated, ie GN is green, BL is blue, BK is black. BK w/TR is black with trace, a contrasting stripe on the wire.

Remember that this is battery (direct) current, so you have a hot side (from the positive + terminal on the battery) and ground through the body. There is no safety ground like you have with house wiring.

 

Another hint, which may be of help - go to the pick-your-part and get a bunch of wire from a newish wreck, or several wrecks. Usually the harness to the rear of the car contains very long wires, though they will be small gauge. You'll have to look for heavier wires under the hood. This is an easy and cheap way to get a lot of different colors without paying a fortune for all those little rolls of wire.

 

What about fire insurance on your rig? Any coverage there? May replace the wiring loom.

 

no insur. it wasent bad,melted half the harness. i worked all summer from frame up to hopefully drive this thing before cold hits. limited money. it aint gonna happen now. i'll take my time with it and redo the wiring work out the other bugs over winter. i really cant afford a new harness. i diden't need this, it took the wind out of my sails.