TheSamba.com :: View topic

Fri Feb 09, 2024 9:30 pm

This question really isn’t specific to this particular forum. I’m just posting it here because there isn’t a general technical forum for electrical questions. (Should there be one? :idea: )

So the basic question is, “Does a wire’s resistance increase with age and usage?”

I have read comments in various electrical discussions that imply that the resistance in wires increases as the wires age and therefore can create problems, particularly in cars with 6v systems. We know that corroded/oxidized connections can increase resistance, but does the wire itself degrade over time and lose its ability to conduct effectively? Cleaning connections and making sure they’re tight has helped solve problems … so why is “50+ year old wiring” getting blamed? Just askin' ...

Sat Feb 10, 2024 12:42 am

"Does a wire's resistance increase with age and usage ?"

I think that is kinda subjective & ambiguous.

ACVWs were budget built. That's why they utilized exposed connectors with crimps, not weather-tite pinned connectors with heat shrink like is common now.

The longer these exposed connections are exposed to humidity, the more corrosion can form.

Age can cause the vinyl jacket to become brittle. This can lead to cracking & allow moisture infiltration. Add to this the back & forth of movement from travel & engine vibration can cause this to accelerate. I guess this could be called usage but rarely are the wires exposed to repeated connecting & disconnecting. Mechanical switches, VRs, & relays can have quite a bit of movement (usage) over their life.

Several years ago I spent almost 3 days cleaning terminals with a rifle bore cleaning tool chucked in a cordless drill and once a year I scrape the major grounds. At least I can rule some things out when diagnosing stuff.

I've fallen victim to the K.I.S.S. mantra too many times !
(Keep It Simple Stupid)

My twisted logic ... stay safe

jinx

Sat Feb 10, 2024 1:03 am

OldSchoolVW's wrote: “Does a wire’s resistance increase with age and usage?”
No.
A little bit of oxidation on the outside doesn't affect the core of the conductors.

Sat Feb 10, 2024 5:21 am

Yes, it certainly does depending on the wire quality. I just went through this trying to troubleshoot a car stereo system. The inner wire was so oxidized that when trying to strip the wires it would just break off like raw spaghetti.

Sat Feb 10, 2024 5:57 am

The copper in wire is basically “stable” — it doesn’t just somehow spontaneously “degrade” over time and/or with normal usage, if that’s what you were asking (?). If it hasn’t oxidized/corroded significantly over the years (i.e. from exposure to oxygen, moisture, etc.), then its resistance won’t have significantly increased either.

So if your old wire’s insulation is still intact and in good shape, there should likely be little or no oxidation/corrosion present in the wire under it, and thus probably not much need to worry about its resistance having increased substantially either. You can always clean the ends and check w/ a multimeter if you want to be sure, though…

Sat Feb 10, 2024 8:22 am

Entropy?

Everything in the universe is going from order to disorder. So, I imagine there must be some minor degrading of the wiring over time. How much, I don't know.

I'm lucky and happy my original wires are still there and working. Over the years I've touched things up with spray lubricants to keep corrosion down.

These cars were not meant to go 50+ years. Most cars were/are not meant to go 50+ years. Whenever I've needed to work on my wiring in any way I've always cleaned things up, soldered, replaced and/or protected as necessary.

I go easy on the more brittle engine compartment wiring if I'm pulling the engine but even there's no problem if you're being careful.

Sat Feb 10, 2024 11:20 am

The wire under ideal condtions in general does not degrade. The valence electrons are still able to move. It is the corroded connections that are the real issue. I clean the connections and apply conductive grease to minimized corrosion.

Sat Feb 10, 2024 3:59 pm

Sorry about the ambiguity, jinx. By “usage” was referring to the act of conducting electricity.

My reason for bringing up the question is that I have seen comments that suggest that the wire itself degrades over time and its ability to carry current is diminished. This didn’t seem right to me since simply cleaning or replacing connectors and/or terminals would, in most cases, improve poor conductivity.

I just wonder if some who are going to the trouble of replacing entire wiring looms are doing so just because they think the old wires have diminished conductivity. I certainly see no problem with replacing old wires that have brittle or damaged insulation or doing a wiring overhaul to correct rampant “creative wiring” done by previous owners. If the original wires are sound though, regular connector maintenance should keep current moving as intended.

As goober and others have said, these cars were not meant to last 50+ years. I wonder just what the VW engineers thought was a reasonable life expectation for these cars when they were new. The practice of planned obsolescence has been around for nearly 100 years, but you wouldn’t guess it by how many older products were solidly built compared to many of the products we use today.

Sat Feb 10, 2024 6:09 pm

No wire does not lose resistance. Corrosion and oxidation cause it. I have pulled out 120v 100 year old cloth covered wire still shiny with wax. Not the same as 12v automotive. As it has no extremes to tolerate, but the wire was perfect.

Sat Feb 10, 2024 6:45 pm

OldSchoolVW's wrote: As goober and others have said, these cars were not meant to last 50+ years. I wonder just what the VW engineers thought was a reasonable life expectation for these cars when they were new. The practice of planned obsolescence has been around for nearly 100 years, but you wouldn’t guess it by how many older products were solidly built compared to many of the products we use today.
Pretty sure that VW’s were designed to last about 10 years and/or 100,000 miles — same as most other cars of that era. Their quality level was actually pretty good, considering their low cost. They were popular for a good reason, and 20 million+ of them sold wasn’t by accident… :-)

Sat Feb 10, 2024 7:02 pm

When I resurrected my 1970 after 23 years of sitting, I just cleaned up the connections on its wires and on the fuse box.

I later cleaned up the grounding tabs for the rear lights.