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Neighbor Jerry, I dont know beans about your tractor but can lay a lil general electrical theory on ya which may or may not help. SENDING UNIT: On most tractors, the sender unit in the tank is a variable resistor controlled by a float on an arm hanging in the tank. Its variable resistance may be from like 0 to 35 or 0 to 200 ohms as the float is raised or lowered depending on the brand. To test it if you placed an ohm meter on its "to gauge" lead and case/frame ground (may be merely the metal or may have a lil grounding terminal) and then raised and lowered the float to correspond to fuel level, the ohm meter should swing smoothly from say 0 to 35 or 0 to to 200 ohns or whatever ohms its designed for. GAUGE: The gauge is a 2 wire series electrical device which receives its hot battery voltage input power from maybe the ON/OFF switch etc., but then receives is return ground path via the sending units variable resistor. That way the amount of current passing through it and its resultant needle deflection depends on how much resistance the sending unit is at any particualr level of fuel. For the gauge to work it needs hot battery voltage on its input lead and to see if it works/deflects you could momentarily dead ground (just brush/touch) its output (to sender) and see if it swings from empty to full. If it swings from empty to full when its output (to sender) is open or momentarily dead grounded, its likely OKAY. NOTE the Gauge MUST be matched with a Sender of the correct resistance range OR ITS NOT ACCURATE. They are usually a matched pair from the same vendor cuz a gauge designed for a 0 to 35 ohm sender wont work right with a 0 to 200 ohms sender. Usually you either gotta get the sender or gauge from your tractor manufacturer so they will match up or else buy a matched generic set (gauge n sender) from an auto parts house. COMMON PROBLEMS: Often if the gauge has voltage on its input but never moves BUT IT PASSES THE SWING TEST ABOVE (says gauge itself is okay), the problem is EITHER a bad/open sender or a poor ground (maybe the tank or sender isnt well grounded, common problem) or an open wire from the gauge to sender, or the float is bad and sinks to the bottom or is broke off its swing arm. This help any????? ?/ John T Nordhoff in Bloomington, retired electrical engineer who usually lurks on the Deere pages versus over here on the dark side lol
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