Dear Vintage - Opel friends,
I'm pleased to be able to offer you the following article:
Temperature sensor coolant display dashboard, Opel rear-wheel drive
This sensor is installed in the thermostat housing of the engine and is suitable for both carburetor and fuel-injection models of all Opel rear-wheel drive models, regardless of whether a cih, OHC, OHV or 24V engine is installed. Please be aware, this part is not suitable for the Opel GT! - It takes on the job of supplying the water-temperature display with the corresponding data.
In case your display still 'plays crazy' after swapping the sensor, you can be fairly sure that your fixed voltage controller is also defective. This is naturally also available in the edelschmiede shop :-)