temp gauge

if you have a ohm meter you can remove the wire from the temp sending unit and look at the resistance from the terminal on the sending unit to the block(ground) I do not know what it should read cold,but you should read something if you get a reading of infinity it is bad.If you can see the gauge with the key switch on quickly brush the wire that went to the sending unit to ground the gauge should react.(it will quickly peg)If it does then chances are the gauge is ok.