RPM gauge drops to zero only when accelerating

[Wex]

I'm experiencing an issue with my car's tachometer. This problem occurs exclusively when I accelerate; the tacho gauge drops to zero. However, it functions normally when I drive calmly without rapid acceleration. To better understand the issue, please increase the volume when watching the attached video. Interestingly, when I connect a computer to the car and access the live sensor data, the tachometer operates as expected across all ranges. Moreover, after disconnecting the computer, it continues to work correctly until the next day. This is puzzling because if the problem were related to a sensor or wiring issue, connecting the computer shouldn't resolve it. Do you have any insights into what might be causing this issue?

 

Video with the issue

[ColinBarber]

Strange one. I suspect it is an electrical fault on the instrument cluster - something like a bad voltage regulator or capacitor so the signal level is too low once it gets past a certain rpm - or the gauge itself is faulty. I'd be tempted to purchase a used instrument cluster on eBay, swap the whole cluster first, then swap the gauge to help narrow down the problem. Otherwise you would at least need to pull the old one out so you can measure voltages whilst it is running.