Broken cables? How does this happen?

I just read another story about it today. A 3-year-old cable “magically” went bad all by itself. How is that? The cable was fine, then it wasn’t. Sometimes, it’s a snap like you see in this picture. More often, nothing looks bad, but the cable just stops working. It’s happened to me, and it’s probably happened to you.

What didn’t happen
First of all, you didn’t “wear out” the cable. People will tell you that a cable “wore out” and actually that’s impossible. Copper doesn’t wear out because electricity passes through it. What’s closer to the truth is that copper will oxidize over time and that can cause problems. Think about that old penny in your pocket, or the Statue of Liberty. Both are made of copper and as copper sits out in the open air it turns brown first, then green. By the time copper turns dull brown, it’s no good for high-end signal transfer.

You can limit oxidation by keeping your connections tight but you can’t get rid of it. Every year, look at the outside of your connectors. The outsides are usually chrome-plated brass, which is more resistant to oxidation than copper. If you see any deep pits or “moldy” looking connections, replace them. A connector that’s oxidized on the outside can be ten times more oxidized on the inside.

What probably causes the problem
Oxidation is a problem, but it’s not the most likely culprit when a cable goes bad. It’s more likely one of two factors (or both): heat and stress.

Heat is a big problem for any connection, but screw-on connections can be especially susceptible. You might know that heat makes things expand, and cold makes them contract. Every material expands and contracts at different rates. When you have a cable connection exposed to heat, it will slowly expand. As it cools, it will contract but as it does, it can slowly become loose, because the connectors cool at different rates, so the one that cools faster may twist slightly. Over time this tiny amount of movement can loosen a cable enough to cause a problem.

When you have a signal problem, looking for a loose wire should be your first step, and it’s a good idea to check the tightness of cables by twisting the connection with your fingers once a year.

Stress is another source of cable problems. Everyone understands stress. Things are going along fine, it’s a hard day but you’re handling it, and then all of a sudden, SNAP — you’re going off the deep end. That’s emotional stress.

The physical stress put on a cable is actually pretty similar. If cables are too tight, they will work for a time but sooner or later some random factor will come into play and something inside the cable will snap. It could be the conductor, or the dielectric foam that insulates the conductor, or it could be part of the connector. You may never know.

Stress breaks can be easy to find in extreme cases, because the cable will snap or come out of its connector. These are rare cases. Most of the time, cable stress breaks are deep inside the cable or connector. The cable looks fine but it’s completely broken.

When heat and stress combine
A broken cable due to both heat and stress can be the most frustrating of all. Imagine if the cable or connector breaks, but it’s just a really small break. As the cable heats up (due to the heat of the day, or operation of the equipment) everything expands “just enough” to let the broken pieces touch. As it cools, the broken pieces separate.

It can also go the opposite way. A loose connection can expand “just enough” to fail when it’s hot and then by the time you test it, it’s tight enough to work. This can be very frustrating and is often the cause of problems where you lose reception during the day but get it back by the next morning.

What can you do?
Sadly, nothing. A good cable tester will help you find problems when you get them, and checking connections will help a little bit. Some cables will last decades while others will fail quickly. At least if you know why it happens, you can look a little more closely for the solution.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.