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Discussion Starter #1
I've got a 1962 Ford f350 with a secondary fuel gauge for the rear tank which is the only remaining tank and it stopped working.ive bought several sending units and most of them didn't work at all but one of them made the gauge move up to a quarter tank when held all the way up in the full position.plz any help would be greatly appreciated.
 

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I'd first check the voltage drop at the sender, then at the level gauge to see if your wires have deteriorated. Have you confirmed theat the gauge is working properly?
 

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I have checked the wiring and it's all good but the gauge worked up until we had a new wiring harness put in and I've had the gauge moving just not where it should have been relative to arm on the sending unit.like my first post says all the way full on the sending unit arm was a quarter tank on the gauge
 

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If I insult your level of knowledge, I apologize in advance. A fuel gauge and it's respective float has to match. Not all floats provide the same resistance at full and at empty, but they have one thing in common, an empty tank will result in a higher resistance and a full tank will be a lower resistance. As much as I can gather, if your gauge is OEM, it's expecting a sending unit that provides about 15 ohms full and 80 empty. That is the rating for an in-cab sending unit, but since they use the same gauge regardless of tank location, I would surmise a mid ship or rear tank should be the same. The gauge, itself works by a heater strip that when the resistance is high, has less voltage going through it and cools causing the needle to move towards empty. A fuller tank will provide a higher voltage to pass through the heater, causing it to heat up and move the gauge towards full. When testing, verify that the float meets these resistances without power attached, then test the actuation of the float with power attached, making sure that it is grounded. If your wiring is good, you may have cooked the heater on the gauge.
 
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