Homemade gauge test tool, C-3826

Both fuel, temp (and sometimes optional) oil gauges have the same gauge movement, so same sender resistance. Your 73 should be the same.

In case you missed it, the reason I used those resistances is because I had some, and because of the switch I used.

Probably an easier better way is to simply buy resistors or combinations of resistors to give you the three needed, then solder each resistor or resistor group to a RadShack clip lead which you have hacked in half.

For example, you can buy four - 100 ohm, 1/2 watt resistors, wire all four in parallel, and that will give you a 25 ohm, 2 watt resistance for the 1/2 scale check.

I've not checked what the gauges draw at full or empty, but I would not buy just 1/4 or 1/2 watt single resistors. I'd think at least 1 watt, but you might get by with 1/2 considering the short time needed.