Help! Temp sender/gauge problem

[grebus1]

Help! Noticed my temp gauge wasn't reading properly, disconnected and grounded the wire that goes to the sender. When disconnected the gauge goes to far left, grounded it goes to far right. Thought that meant gauge and wire were OK, so replaced sender. Now gauge goes almost to red area when engine is warm. Kitchen thermometer in rad shows about 180. Do I have the wrong sender or is there possibly another problem? Already replaced thermostat and rad cap.