bouncing gauges on the dash

[chrisbmwe30]

my 1991 e30 318is has a problem with the tacho not responding and the speedo jumps up above 45km/hr and begins to read but will drop at any given time. also the temp gauge bounces not like an increasse of coolant temp but bounces back and forth a little very quickly, i have just finished a complete rebuild of the motor and installed all new temp sensors so that rules that out for why the temp gauge bounces. where are all the speed sensors speedo cable are and how to check there operation. this problem was also present before the motor rebuild.
thanks

[Dj Buttchug]

is the battery dead? or dying?

[Jboss12]

I'm not sure why all of them are bouncing but I remember when my speedo was messed up it was because of the sensor that plugs into the diff. It was all covered with gunk. When I was driving on the freeway it would randomly start bouncing up and down then stop working all together. This is for an e36 though but I'm pretty sure they have the same location for the speedo sensor

Either that or what buttchug said

[bmwm42]

Crappy board replace cluster

[nomansland92]

Mine did this with the temp gauge when the group was bad.

Check all the connections before you buy anything