190xt gas gauge ?
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Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=14617
Printed Date: 28 Sep 2024 at 5:43pm
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Topic: 190xt gas gauge ?
Posted By: Bob (mo)
Subject: 190xt gas gauge ?
Date Posted: 02 Jul 2010 at 8:18am
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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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Replies:
Posted By: Bret (OH)
Date Posted: 02 Jul 2010 at 11:07am
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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.
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Posted By: Skyhighballoon(MO)
Date 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
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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
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