There are two sending units. One has two electrical terminals, and is in series between the other sending unit, and the fuel guage. (Been there, fixed that!)Starting from empty, the bottom sender causes the gauge to move to about 1/2 tank. The resistance of the lower sender then remains constant, and, as the upper tank begines to fill, the float in that tank begins to rise and the sender unit in that tank begines to change resistance, causing the gauge to begin moving upward from 1/2 towards full. The sender with one insulated terminal needs it's metal frame grounded for the system to work, and both floats must be intact, and free to move, and both senders need to have electrical continuity that changes with float position, for the system to work. I do not have an IH manual for this, but the local town uses one of these tractors for maintenance, and we service it. They have the IH manual, and the gauge circuit is spelled out in detail. I would recommend having the manual at hand, or see if the dealer will copy the pages pertaining to the fuel gauge.
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