My temperature gauge recently quit. For the first few weeks I owned the car, the gauge worked fine but jumped a bit if mashed the accelerator and let off. Now it doesn't work almost at all. When I turn the key to run, I can see the needle jump from it's resting place to right below the first mark, but it doesn't normally move from there. I changed the temperature sensor right by the upper radiator hose and that didn't fix the problem, but now the electric fan always kicks on when the car is barely warm. Also, once in a while, the needle will dance around while I'm driving, sometimes reporting the correct temperature for a few moments. I know there's a temperature sensor in the WUR, does that feed the gauge? Or is there some other temperature sensor on this car?

__________________
1987 300SDL