Temp gauge reads with lights on

[surfsup]

My temp gauges pins when I turn on head lights (no key in ignition) when I start the car it seems to read normal but not really sure if it’s correct, has this happened to anyone else not sure if it’s the gauge, ignition switch, or a dreaded short some where, and if I take the wire off the sender it still pins when I just put the lights on
92 lx was a 2.3 now a 302