Does copper wire go bad?

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dibbons

dibbons

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I was fixing a side marker on a 1972 Plymouth project car today. When I when to strip the old factory wire to make a connection, the wire came off along with the insulation, this happened two more times when I decided to use a razor blade instead of the wire strippers. It seems the copper wire all the way up, even though it is still covered in factory insulation, somehow got weak and fragile. What gives? Does the copper wire have a life expectancy of some kind? Oh, as a side note, I found with my digital voltmeter showed that both rear side marker wires were only reading 10 volts at the bulb socket (with the motor off). I wonder why it's not reading 12 volts? Thank you.
 
If it gets too hot it will get brittle, but it would have to be hot enough to the point that the insulation would have melted.
 
There are a few things that can happen. Copper work hardens, the more it is bent, the more brittle it becomes. Corrosion from salt, and other contaminants also damage copper. Nicks in the copper will also result in strand breakage, best to use correct wire strippers, that only cut insulation, and not nick the copper.
The low voltage readings, may result of poor connections in the harness. Best to find a factory service manual, and find all connection points. Housing grounds important too.
 
The initial quality of the copper is a player also. No guessing what mix or quality control was used back then.
Low voltage could be in the park lamp circuit alone or could be found throughout the vehicle. Best place to begin diagnosis ( for me ) is the fuse box. If only the park lamp circuit is weak ? If all hot at switch on circuits are weak ? If both hot at switch on and the hot at all times circuits are all weak ?
Each condition leads to a different place.
Good hunting.
 
Copper wire will go bad. It will start at the connections and work it's way back into the wire. It will change green and black and will have high resistance. This is usually with fine stranded wire and not the bigger solid strand wire. Electricity flows on the outside of the wire and not thru the center so when it gets corroded and oxidized it will create resistance and make heat and the corrosion will spread faster into the wire. I had a bronco 2 that had badly corroded starter wires and it would start intermittently and took me a while to find the problem because it was inside the sheathing and you can't see it until you strip the wires insulation.
 
I;ve wondered the same thing. One of my tests, bend the wire all the way against itself, if the plastic insulation around the wire cracks, then I toss the wire.

Also what about seeing a little greenish on the copper wires when you strip it? Does that mean the wire is going bad?
 
Usually once it starts going green it can be spread all through it so if you cut it out it could be bad up further also.
 
Update:
Even with the motor idling I only read 10 volts at the rear side marker lights. Battery voltage is 12.4 (motor off) 12.8 (motor idling), and 14.1 (fast idle). The voltage at the rear side marker lights goes up to over 12 volts at fast idle. The turn signals flash at the current rate but very weakly at idle and at fast idle that brighten up quite a bit. Am I due for a complete wiring harness upgrade or could it be a charging systim glitch? Anyone else have similar symptoms and found the correct fix? Thank you.
 
Have you checked connector in drivers side kick-panel, ahead of door? It is what feeds the rear lights. There are also likely connector at side light feeds too.
 
Update: I did some more testing. Simply by raising my idle speed from 600 RPM to 750 RPM it brought the voltage at the battery from 12.8 to 13.5 volts. That was enough to get all the blinkers flashing correctly at idle. I didn't realize the alternator/voltage regulator were so sensitive to idle speed changes, maybe just due to everything now is 45 years old.
 
I see you have a gen1 Barracuda so you've probably got a non squareback alternator & I I am not surprised at your voltage readings. The old alternators didn't do well at idle speeds but they sorta work ok unless you have a weak battery.
 
^^^^^^^^^^^^^^^^^
All this is is why I have been preaching for years to deaf ears!

Most of our cars are or approaching 50 years old. Replace it. My choice M&H! I drive knowing every strand of wire is new and less likely to start an issue that can lead to total meltdown! No shortcuts or add-ins on original type wiring without without understanding the additional load and possible impacts! I have seen reports of issues with M&H but believe the wrong piece was ordered. These cars differ from year to year slightly, Models, makes and years were all slightly different. Do your research and order the correct piece. I started stripping back my old harnesses just for giggles and was not surprised to see lots of green and black badness. I do not know if the repro stuff will last as long but comfort in believing it may!
 
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It seems most of the wiring is fragile and black so 1969383S is right, wiring that is over 40 years old just won't cut it anymore, but it did a good job unitil now. Others working on projects should consider not skimping on wiring, I should have known better.
 
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