Temp gauge mystery

. Also, my sender reads 318 ohms cold engine. 24-28 ohms hot engine, depending on whether the t-stadt is open or closed. Technically, these readings are outside the parameters listed by Dana67, but close
Those are spot on. 300 is greater than 73 so cold is anything greater than 73.

As for 24 to 28 that's as close to 1/2 scale you can get.

Run it?