Grounding problem Thema V6 S2

[Daniel]

Just today I bought a Thema V6 S2. It seems that the speedometer has a grounding problem (speed changes in dependence of indicators and other consumers).

Could anyone tell me which grounding point is used for the speedometer (and the location) ? Thanks !

[Daniel]

Meanwhile I could make sure that the grounding problem is not caused by battery contacts, battery-to chassis-connection or the generator. I am convinced that it is only a problem of the speedometer area and connected cosumers (i.e. indicators).

The voltmeter in the speedometer displays 9-11 volts, changing in dependence of the activated consumers (like mentioned above).

There is a grounding point leading through the dashboard. From the engine side it looks to be o.k. (has also full battery voltage). I presume that this grounding point is mainly used to connect the dashboard to the chassis.

Does anybody knows where the speedometer is connected to the ground ?

Thanks, Daniel.