While cutting hay I noticed the temp. gauge needle closer to the red area than it normally runs. Little while later the needle moved all the way to the red. Went to the shop and loosened radiator cap. Barely a little puff of pressure on the radiator. Coolant almost to the top. No steam. I believe the gauge is wrong. Gauge needle stays all the way to the right (indicating very hot) even when engine is completely cold. Removed the wire from the sending unit, no change. Is there some checking to determine the cause of the gauge not registering properly or could it be something besides the gauge.