If your gauge hangs up at either corner or just hangs in the middle (at 200)...watch the needle when you start the engine.
I found that my needle is just pivoting at the bottom where it attaches to the gauge internals.
I haven't taken the thing apart tofix it yet, but I assume the needle has two pegs on the back that insert into the gauge assembly and one of mine is broken or sheared off.
I know the gauge itself works because if I just let the car warm up without driving it, it registers correctly. It's the first bump I hit or closing the door that sends the needle to the center where it stays.