Temp guage problem!!

[67stepside]

I have a 67 that has been swithed over to a guage cluster. I have switched all of the wires in the cluster plug. When I turn on the key the temp guage jumps all the way to hot and as soon as it starts it goes back to cold. The wire from the guage goes to the ignition switch and then to the cluster. If I run a wire from a grounded temp sensor to the guage and bypass the ignition I can heat up the sensor and the guage will move as it is supposed to. Do I need to bypass the ignition for a proper hookup? Thanks