my pickup truck does the same thing after about 80kph the needle just wanders from 80-120 randomly.
at one point i got fed up with it took the dash apart and cleaned the back of the cluster, checked all the connections and put it back together. the connectors on that cluster are flimsy as hell and it only worked temporarily.
i would start there the e36 has much better connections on the cluster then my truck would suck to be throwing money away because of a loose wire.... a bad ground can also cause weird electrical gremlins.... could also be a bad cluster? but im unsure of a wy to check that other then trying another cluster and if the cluster you use has a mileage difference of 10k or more you will get a true mileage unknown dot on your cluster so unless you can find a cluster with similar mileage to your car id save that for last the e36 gauge cluster also has a fairly low failure rate i believe
e36 parts for sale pm me
Last edited by Steve420; 09-30-2014 at 10:56 AM.