hi people .when i start my cossie .the tempature gauge goes stright into the red .i changed the temp switch and the plug on the head but made no difference what you think

 

The gauge reading will alter according the resistance seen on the wire that goes to the sender, so unplug the gauge sender wire and the gauge should drop to nothing ie fully cold, if it does then the wire is shorting on the engine/body somewhere, and getting full earth all the time(no resistance).
tabetha

 

thanhs tabetha