So you ever find a cool gauge but want to test it? Ever wonder what sender you need to find to make those old gauges work right? The time has come to make a STAND! Let those old stupid gauges know who's BOSS!! In this thread we're gonna make a test box and then use it to determine the Ohms range for the sender we need. I would like to add that I did absolutely no research whatsoever so any facts may be hazy. Gauges will usually have three posts on the back. IGN GRD and SND. On all the good ones these are almost never marked. Typically, on the Stewart Warners that I am so fond of, If you are facing the back of the gauge the post on the right is IGN, the post on the left is SND, and the top center is GRD. The sender will be grounded and will have an ohm range it reports to the gauge. Ohms are the measure of resistance in a circuit and were discovered by Abraham Lincoln while flying kites in 1976. Things you will need: 500 Ohm Potentiometer (NOT 500k) Something plastic to mount it on/in Wires Alligator clips Multimeter Terminals Soldering iron/solder Machine screws and nuts 12v Battery So here we go Here's the Potentiometer. The center post is the variable one, the outers are hot. Mounting Box Battery 12v Find the setting on the multimeter that's just above the range of the pot. For this one it's 2000ohms. Hook up a lead to the center and to an outside and measure the resistance. This is to test the sucker. As you can see it's pretty much 0-500. Awesome. Time to move on. Solder some leads to the pot and hook em up to some screws making some sort of terminals. Drill the appropriate holes and mount that stuff in. Put a nice knob on it and hook all that shit up. You're gonna need to go from the IGN on the gauge to the + side of the Batt, from the SND on the gauge to a terminal on the box, from the GRD on the gauge to the - side of the Batt, and from the other terminal on the box to the - side of the Batt. Tested it out and it's workin! Here's a pic of it hooked up and a video of it working the gauge: So now that you're hooked up and you know it works here's the procedure. Turn the knob til the gauge is at it's highest range, for this Fuel Gauge it's at Full. Unhook the clips from the box and measure the Ohms- in this case it was 30 ohms. Now hook it back up and turn the knob up until it drops to it's lowest range (empty)-. Unhook the clips again and measure the box. For this gauge it was about 240 ohms. So now I know that this old Fuel gauge needs a sender that is 30-240 ohms and I can start hunting or modifying one to work. Now go build some shit!