I might point out here the 30 - 240 ohm resistant gauge movement is electrically the same regardless of the whether the faceplate reads oil pressure, water temperature, or gas level, the type of 30 - 240 ohm resistance sender unit is what determines what the gauge will be used for i.e. if you have a gauge with a temperature faceplate and want to use it for a gas gauge all you need to do is hook it up to the gas tank sender and put the gas faceplate on it. Changing the faceplate on a sealed cup gauge may be pretty difficult, on the cluster type gauge board it is just a matter of 2 screws once you get the gauge out of the pod.
For temporary use you can just hook up to the appropriate sender and readout the gas level, oil press, or temperature by seeing where the pointer is in the range of the faceplate disregarding the numbers or letters. Temporary for me is generally about 5 years when I do that.
Different brands use different resistances ratings, the resistance valve of the gauge must be the same as the sender, 0 - 100 ohm gauge movement will require a 0 - 100 ohm sender. You can determine a gauge resistance rating required by reading out the original sender on you tractor by removing the gas sender from the tank, connect one lead of the ohm meter to the terminal and the other lead to the flange, lift the float full travel the meter will read the resistance range of the wound resistor. All but one major brand (can't think of the name) uses the low resistance as full and high resistant as empty. Resistance readings are nominal, gauge may read full at 20 ohm and empty at 230 ohm or any other combination, They are just ballpark instruments.
I might point out here the 30 - 240 ohm resistant gauge movement is electrically the same regardless of the whether the faceplate reads oil pressure, water temperature, or gas level, the type of 30 - 240 ohm resistance sender unit is what determines what the gauge will be used for i.e. if you have a gauge with a temperature faceplate and want to use it for a gas gauge all you need to do is hook it up to the gas tank sender and put the gas faceplate on it. Changing the faceplate on a sealed cup gauge may be pretty difficult, on the cluster type gauge board it is just a matter of 2 screws once you get the gauge out of the pod.
For temporary use you can just hook up to the appropriate sender and readout the gas level, oil press, or temperature by seeing where the pointer is in the range of the faceplate disregarding the numbers or letters. Temporary for me is generally about 5 years when I do that.
Different brands use different resistances ratings, the resistance valve of the gauge must be the same as the sender, 0 - 100 ohm gauge movement will require a 0 - 100 ohm sender. You can determine a gauge resistance rating required by reading out the original sender on you tractor by removing the gas sender from the tank, connect one lead of the ohm meter to the terminal and the other lead to the flange, lift the float full travel the meter will read the resistance range of the wound resistor. All but one major brand (can't think of the name) uses the low resistance as full and high resistant as empty. Resistance readings are nominal, gauge may read full at 20 ohm and empty at 230 ohm or any other combination, They are just ballpark instruments.
The 30 - 240 ohm Steward Warner gauge, and typical of resistance gauges, internal movement and wiring connected to a 30 - 240 ohm sender are as this pic regardless of what they are used to measure. The pic view is from the front of the movement. Viewed from the back of the gauge all SW resistance gauges in this era, right terminal is power from switched source normally the ignition switch and left terminal is out to the sender. Most brands are connected like that but you will need a wiring diagram for other brands to be sure or just check another resistance gauge of the same brand on your tractor. The power coil circuit is grounded to the pod or cup to complete the circuit. The current flow through the sender coil is varied by the sender increasing or decreasing the strength of its pole magnetic field opposing the strength of the power coil pole magnetic field which remains constant and so moving the gauge pointer via its pole.
Joe