VDO RPM indicator on 912 ULS

faced with this problem, did anyone try the 150 ohm resistor on the rpm sensor coil ??

Since it is intermittent it would seem that you have a bad wire or connection problem. I had an intermittent red cube flow meter. I crimped on new connectors in the circuit and the problem was resolved. The intermittent problems are the worst.

intermittent failure every two to three months!
I will check the connections, check the grounding of the cable, and look at the oscilloscope for the "cleanliness" of the sensor signal.
I think first of all about a problem of electrical noise.
I would return to the forum to talk about the solution, if I find!
meanwhile, RPM breaker on / off 2 seconds, it's not critical to flying, but not perfect.