fuel gage ?
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fuel gage ?
hi i am new to this forum and to the wounderfull world of ford trucks. i just picked up a 77 f250 w/ 460... i have solved most of the issues that allowed me to get it cheap. rebuild carb pwr sterring leak fixed rewired rear lights. but when i was under the truck i found someone had hooked the fuel sending unit wires to the right turn signal wire. i corrected this or so i thought. now it just reads empty all the time. i am normally good with electonics and wireing but this has me stumped. i can't seem to find a fuel sending unit wireing diagram anywere but one wire should go to the gauge the other to ground right? any help here would be great... thanks
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No. The sending unit is the "ground" for the gauge. The gauge is fed a regulated 5v from the instrument cluster circuit board. The regulator on the circuit board feeds all the guages.
The other side of the gauge (you can consider this the "ground") leaves the instrument cluster and goes down the frame to the sending unit. The sending unit is a variable resistor, with one side hooked to the wire going down the frame, and the other side grounded. The sending unit varies the resistance to ground, and this makes the gauge move back and forth.
The easiest test to perform is to find the correct wire running down the frame to the sending unit, and with the engine off but the keyswitch in run, ground this wire. The guage should swing full scale empty or full. Then take the wire off ground and let it hang in the air. The gauge should swing full scale the other direction. If it passes this test, then the guage and the wiring are good, and there is something wrong with the sending unit and or the grounding to the tank/sending unit.
The other side of the gauge (you can consider this the "ground") leaves the instrument cluster and goes down the frame to the sending unit. The sending unit is a variable resistor, with one side hooked to the wire going down the frame, and the other side grounded. The sending unit varies the resistance to ground, and this makes the gauge move back and forth.
The easiest test to perform is to find the correct wire running down the frame to the sending unit, and with the engine off but the keyswitch in run, ground this wire. The guage should swing full scale empty or full. Then take the wire off ground and let it hang in the air. The gauge should swing full scale the other direction. If it passes this test, then the guage and the wiring are good, and there is something wrong with the sending unit and or the grounding to the tank/sending unit.
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thanks, that helped alot... i had to run a new wire from the dash down to the sending unit but it works now... some one hacked my wires from the tank back i spent all day rewireing all of it just to get the turn signals to work... thanks again
