Might want to start a new post. Or read this one. I have the same issue in my 5210. It reads halfway with the key on, completely cold, and runs up to the red when tractor is at operating temp. I replaced the gauge to no avail, which leads me to believe it is the instrument cluster. My fuel gauge hasn't worked right for years. As long as my tachometer and hour meter are working I'm not gonna mess with the instrument cluster. I'll install an after market temp gauge before I attempt to break (fix) the cluster. For now a cheap laser temp gun works for me.