How do I test my instrument cluster?

Do it right. You need to read this thread........

Printed circuit pins repair

You need some resistors or a variable resistor such as a fuel sender that you can adjust to different resistance to act as a sender

c-3826-jpg-jpg.jpg

You need to use a battery NOT a charger, and figure out how to substitute resistances shown in the photo for each sender. All 2 or 3 gauges should read the same with the same resistance, they are the same gauge movement.