1995 C280 Water Temperature Gauge
 

The water temperature gauge on my wife's 1995 C280 began acting intermittantly yesterday. I checked the connection to the water temperature sending unit and this appears to be OK. I was thinking about replacing the water temperature sending unit next to see if this is the problem. However, before ordering the part, I thought I would check to see if others have encountered this problem and if there is anything else I should check first.

Mostly during the winter months, my temp gauge (and occasionally tachometer) usually stays in the resting position for a few minutes or until I whack the dashboard. The needle sticks to the resting knob... something to do with the paint MB used.
Does your gauge work on and off? Or does it not work when first starting the car... and then kicks in again?
If your problem is like mine, I'd be pretty sure about the sticking needle.

The needle does not work upon initial starting and then starts working after the engine has warmed up. Yesterday, the car was parked outside with a temperature of 29 F. It took about 15 miles of driving before the needle moved all-of-a-sudden to normal position. This morning with the car parked in a 50 F garage, it only stuck for a short while.

Yes, I have also had the gas gauge needle stuck(?) in the resting position, but that also comes back if you are a little patient and wait for it.

It could be that the needle is "sticking" to the lower post as you suggested. I will monitor for a while to see how it behaves. I guess the temperature sending unit is working if the gauge eventually rises to normal position.

Yes... try whacking the top of the dash a few times... mine usually rises if I do this.