190xt gas gauge ?

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   On my 190xt i put a new fuel sending unit in and the gauge worked but it was in bad shape so i bought a new stewart warner fuel gauge and the only way i can get it to work is with the wires hooked up to the gauge like they should be when i touch the grounded test light to the sending unit pole it works when i take it off it goes all the way empty .I tried just a straight piece of wire from a ground to the sending unit pole and the needle goes all the way full . I have checked all my wires and everything seems to be correctly hooked up and in good shape.Iam totally stumped .Can anyone tell me what iam doing wrong?Thanks,Bob

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Bob (mo) Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 22 Nov 2009 Location: Missouri Points: 140	Post Options Post Reply Quote Bob (mo) Report Post Thanks(0) Quote Reply Topic: 190xt gas gauge ? Posted: 02 Jul 2010 at 8:18am
	On my 190xt i put a new fuel sending unit in and the gauge worked but it was in bad shape so i bought a new stewart warner fuel gauge and the only way i can get it to work is with the wires hooked up to the gauge like they should be when i touch the grounded test light to the sending unit pole it works when i take it off it goes all the way empty .I tried just a straight piece of wire from a ground to the sending unit pole and the needle goes all the way full . I have checked all my wires and everything seems to be correctly hooked up and in good shape.Iam totally stumped .Can anyone tell me what iam doing wrong?Thanks,Bob

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Bret (OH) Members Profile Send Private Message Find Members Posts Add to Buddy List Silver Level Joined: 15 Sep 2009 Location: Blanchester, OH Points: 347	Post Options Post Reply Quote Bret (OH) Report Post Thanks(0) Quote Reply Posted: 02 Jul 2010 at 11:07am
	Gauge and sender unit need to be matched with regard to resistance. If you are using an Agco sender you will need to use an Agco gauge. If you want to keep the SW gauge it will probably need a SW sender. The way it works is the sender supplies the gauge a ground. Empty tank provides the gauge with zero or very little ground. As the tank unit moves more towards full the gauge is supplied with an increasing amount of ground. Thus, when you ground the terminal on the unit with a wire it is supplying a full amount of ground and the gauge reads full. When you touch the terminal with your test light the ground is running through the bulb which offers a resistance thus a decreased amount of ground and the gauge reads somewhere below full. You may be able to figgure out what added resistance is required in the circuit to make the gauge read correctly and add a resistor in the wire going to the gauge, but it would be though to find the value needed for the gauge to read correctly at all fuel levels.

Skyhighballoon(MO) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 11 Sep 2009 Location: Pilot Grove, MO Points: 3115	Post Options Post Reply Quote Skyhighballoon(MO) Report Post Thanks(0) Quote Reply Posted: 02 Jul 2010 at 11:16am
	My way to simplify it is to think of the sending unit as a variable resistor and the gauge as a ohm meter measuring it. Like Bret says, that gauge has to match/be calibrated to the sending unit for the readings to be accurate. Bob - I've picked up working used Allis gas gauges from Cooke Tractor in Clinton, MO for $5 each in the past. Not sure of the going rate now. Mike
	1981 Gleaner F2 Corn Plus w 13' flex 1968 Gleaner EIII w 10' & 330 1969 180 gas 1965 D17 S-IV gas 1963 D17 S-III gas 1956 WD45 gas NF PS 1956 All-Crop 66 Big Bin 303 wire baler, 716H, 712H mowers