Not really sure if I should post in this sub-forum, but...
I have an instrument cluster from a car which no longer displays the vehicle and engine speed on the gauges. When you start it up the speedo starts oscillating and the tacho does not move at all. When driving, the speedo continues to oscillate and the tacho stays on zero.
If I open up the cluster and turn the needles so that they are no longer on the zero position (i.e. speedo shows e.g. 120km/h and tacho 4000rpm) and then power it up, the dials return to the zero position but oscillate while doing so. Once they reach zero they stay there (but with the speedo needle still oscillating).
Both dials are driven by stepper motors (each motor has 4 contacts). The stepper motors are controlled by a microprocessor.
So my question, does it sound like the stepper motors are the problem or could it be something else? It is strange that both would fail simultaneously. It has worked intermittently a few times over the past few weeks, but it is always either both gauges working or both not.