Ever Wondered Why the Fourth Pin on Your Lightning Cable Turns Black? We Found the Answer

Lightning cable black pin

Have you ever had a lightning cable whose 4th pin (or 5th depending on which side you are counting from) turns from golden color to black? If yes, then you are certainly not alone. Over the years we have all had lightning cables that have shown burn marks and black pin.

Today I stumbled upon a Reddit post in which a guy asked the community why does his lightning port’s 4th pin has turned black. After reading his post and looking at the picture that he shared of his cable, I looked for one of my older iPhone cables that had the similar black spot.

Turns out it is something that is quite common and many people have seen lightning cable corrosion judging by the respondents on the Reddit post.

Why Fourth Pin On Lightning Cable Becomes Black

Luckily another Reddit user who introduces himself as an electrical engineer explains the reason behind 4th pin turning black from gold. According to the user it is a common electrical phenomenon.

He explains that the pin or the ‘terminal’ either has a positive or negative voltage connection. When the connector is plugged into the iPhone or iPad’s lighting port, there can be a small spark gap that happens when the cable is connected with the device.

The likely cause for this is due to a capacitor charging and drawing more current for a fraction of the second. Since the electric current is able to jump between the plates easily, this overtime causes the copper to erode, making the pin appear black.

He goes further by suggesting to clean the cable with alcohol, which may make the black side of the cable functional again. We haven’t tested his solution of cleaning the cable with alcohol so can’t confirm if it works. You are welcome to comment below about the result, if you give it a try.

In many cases when the pin becomes black, one side of the lighting cable stops working. This is certainly true in my cable’s case as I can only charge and sync my iPhone from one side of the cable as other ones doesn’t work at all making the problem particularly annoying. [Reddit]

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  1. Just returned an iPad to Apple for just this reason … I was on the 4th cord and the damned things aren’t cheap. Rest assured if this thing is burning the cord plug, it is also burning the interior contact. It is an engineering flaw and needs to be fixed!

    1. Yup, poor design. Cable should have something like a pre charge resistor to prevent the spark that burns up the 4th pin.

      1. You could well be right…,also I thought these connections were all gold plated… I have several cables but this problem does not occur on all of them. From that one could infer that it could be the thickness of the gold plating. Though just guessing. I had the same problem with normal Ethernet cables in a higher than normal power draw application. Advised by the supplier of the equipment to try a higher quality cable which had superior connection terminals. After this never had a problem again. From a visual inspection looked as though the gold plating was thicker though it may also be that the terminal under the gold plating maybe better quality lower resistance and possibly with less heating. With the lightning cables though this problem for me has occurred on the more expensive cables eg apple ones. It needs someone to investigate the thickness etc of the gold plating etc eg is the gold plating thickness inversely proportional to the rate of the problem .
        Very careful cleaning can return the functionality of the cable but probably won’t last long as the gold plating will probably be perforated to the underlying much more easily oxidisable probably copper layer. Which is probably what is happening also with a too thin layer of gold exacerbated by the higher current draw on that terminal. As I say I’m only guessing. These early failures of these charging/data cables must be severely adding land fill, resource usage and is not acceptable when it is considered the vast number of phones etc out there.

  2. The black burnt pin problem is easily prevented by first switching off or unplugging the 5volt wall-wart power supply before inserting the lightning connector into your iPhone or iPad. Also switch off the wall-wart when charging is complete before unplugging the lightning connector. This ensures that current only passes through the delicate lightning connector when it is firmly fitted into its iPhone. Sadly this only works with a new connector – once the pin is burnt it can not be repaired. At least with a lightning connector the damage is clearly visible but the proposed new USB ‘C’ connector has completely concealed pins so an eventual failure to charge will be the only symptom.

  3. Tried the alcohol clean- didn’t work, but glad to have an explanation-was driving me mad why sometimes charge worked and at other times didn’t- obviously depended on which way I put the lightening connection. While it might be worthwhile hanging onto a cord that has the problem and remembering which way to insert, I’ll be tossing mine.

  4. An alternative to Hugh’s suggestion is to connect the cable to the phone before connecting the USB plug to the charger. The solid lighting connection will then not be subjected to any spark at initial connection, the beefy USB plug taking the hit. Try with a new cable and see how long it lasts.

  5. The cable companies, stress on the cable itself saying we have the strongest cable, but that’s not the problem. The problem lies in the pens and that the plating is too thin, which, eventually they can get burned what they need to do is double plate or triple plate them

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