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Carbon or Silver?

Which one should I buy - silver or carbon ribbon cable?

At BMW E38 E39 X5 speedometers and MID displays, it is very common that the pads of the LCD have interrupts (apr. 30% of the cases the LCD pads have interrupts). This is due to the heat bonding procedure applied in the factory when it was assembled for the first time. When you remove the original cable, some parts of the LCD pads will come off too, just like on the picture on the right:

This is how a good LCD looks like (70% of the LCDs look like this):

And this is one with interrupts (30% of the LCDs look like this):

What to do in case you have an LCD with interrupted pads? Well you have 2 ways to go.

1. Buy a SILVER ribbon cable that works fine even if most of the pads are interrupted. Carbon will not work this case.
2. Buy a new LCD plus a new ribbon cable (carbon and silver will both work)

What is the difference between carbon and silver cables?

Well the most important is that silver has 10x better conductivity, and makes a much more robust and reliable contact. This is a very important parameter as you may imagine if one of your 120 conductive traces has a 1 ohm, the other has 5 ohms resistance in your ribbon cable. You will still see all the pixels, but the screen will be very uneven, some lines will be brighter, others will be darker... That is why all professional flexible cables are made of gold, copper or silver. Up to this point, carbon is NOT USED AT ALL in any OEM applications, so none of the speedometer manufacturers build them in, only silver, copper or gold.

You may bend a silver cable 500 times and it will still work, bending 15 times a carbon cable could cause problems. As you are a DIY-er, you may need to do 3 or 4 attempts until you get your unit fixed, during these tries you may bend the cable several times, so the more robust is better.

Heat: The other important parameter is heat cycling. All car components have to withstand heat cycles as aggressive as -20 to 85 degrees Celsius. Just imagine a cold winter when you start your car in the morning in -20C cold and it reaches the 85C operating temperature well this is what the components have to withstand something around 2000 times during the 10 years lifetime. That is why it is important to know that if you buy a cable that withstands much more heat cycles (silver withstands up to 3 times more heat cycles) it is more likely that you will still have all your pixels after 2-3 years.

In summary: We only recommend buying the carbon cable to all those with low budget and those who are 100% sure that the LCD pads are in 100% perfect condition, there are no interrupts on them. And also for those who are not planning to keep the car for very long. To all others Id day its worth it to spend 15% more and get the right product.

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