Temp gauge Not Working

[Ardee83]

So I have done a little bit of reading, but I still cant seem to nail down the issue.

I installed a new crate 350 motor about 2 years ago. I put everything new on it that I could and that included the temp sender. The temp sender was working fine, then one day just stopped working. It just reads cold as if the truck is never heating up. I grounded the wire and it pegged all the way over to hot. So I figured it was the temp sender, ran to Napa picked up a new one. Installed it and the same exact thing, gauge still reads cold. So I again grounded the wire and same thing, pegged all the way to hot. So now I am at a loss of why it just suddenly stopped working. Any thoughts?

1983 Chevy C10 350.