I got the 10V converter today. Hooked it up to a 13V source and got 9.98V out. Good to go.
I pulled the water temp gauge and sensor out of the car. Applied 10V to it with the sensor in boiling water. The needle never moved. I then retested it with 12V. Needle never moved. I think the sensor is bad. The gauge does a full swing when initially hooked up.
Tomorrow I will do the bench test on the
oil temp gauge and sensor.