Alright guys, I left work and the car was already warmed up (1978 280Z) the temp was about a quarter of the way to half way on the gauge. I stepped into it and then when I got off of it the temp gauge suddenly shot down and stayed there. I pulled over checked the wires and everything seems to still be connected and in tact. Any ideas to what has happened? Thanks in advance guys.

sender unit gave way, or corrosion at the connector, bad connection, i think