Just installed a new thermostat in my 06 s/c due to the gauge not rising much, the original stat was shot! This did cure the issue and the gauge moves up to the 3'o'clock and stays there all day!
On occasions the needle seems to stick below the blue section of the gauge and won't move? If I turn off and back on the gauge jumps straight to its normal running temp 3 o'clock position!
It once started to rise up the gauge only to shoot down to below the blue for some reason but again stop,start and it goes back to 3 o'clock Any ideas

Well it sounds like a mechanical issue with the gauge doesn't it.