Howdy folks, my (A3 8l 1998)temperature gauge seems to have stopped working. I'm still getting warm air in the cabin but not exactly that hot that I need to turn the temp setting down. Currently set it at 29 degrees and it's warm not unbearably hot. It also takes a while to get warm. The temp gauge isn't going up at all. What do the experts think? Thermostat? Or Temp Sender Unit? Possibly both? Any help opinions, Thanks.