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John T
03-03-2001 08:28:06
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Re: Checking 3020 diesel fuel guage in reply to John S., 03-03-2001 07:42:10
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John, Im not positively sure of the gauge on your tractor, but generally, that type of gas gauge circuit works by applying a voltage to the gauge, then current travels through it (deflecting the needle) to the tank sensors variable sliding resistor, then to case ground on the tanks frame. Therefore, if you have voltage present to the gauge (you gotta have that first for it to work, so check that out) and its got continuity through it, if you momentarily ground out the wire leading to the tank and the needle deflects, the gauge is good but the sending unit is bad or its not getting a good ground. If the gauge has voltage on one side and you ground the other side and it never moves, its likely bad. Also, the gauge needs electrical continuity through it. The sensor on the tank is just a variable sliding resistance to ground, and it also requires continuity to the frame somewhere which is usually the little black wire screwed to the tanks frame. So, check for voltage to one side of gauge, temporarily ground other side very briefly to see if needle moves (if so gauge is good), then see if the tank unit has continuity and gets a good case ground. In my experience, its usually a bad tank sending unit. Ol John T
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