AFTERMAKET FUEL GAUGE

[57fordf100]

hey guys so i connected the after market fuel gauge connected it to the fuse running 12v connected the ground then i connected the wire from the tank and it started reading im not sure if its right everytime i turn the key it says i have less gas lets say i turn the key it says i have half a tank turn the key off then turn it back it will read less then half a tank what can be causing this would it be the sending unit? any help would be great thanks guys

[BobbyFord]

Let the gauge heat up for a few seconds when you power it up. Why are you running an aftermarket gauge?

[57fordf100]

my old fuel gauge didnt work for nothing and i didnt have the cash to have it rebuilt i have a 1957 ford f100 im thinking about getting a 12v sending unit i found them for 50 bucks but i mean if it works with the stock sending unit i might as well keep it

[fordman]

the stock fuel gauge is supplied power from the ipvr . i do not know if your new gauge requires a full 12 volts or what. the ipvr is suppose to give out 5 votls.

[Thunderfoot]

I agree with Bobbyford let it warm up a bit and see if it stabilizes.
It depends on your aftermarket gauge as to what Ohm range it is supposed to be reading as to the accuracy of the gauge, all the sending unit is - is a variable resistor and the gauge reads the resistance and displays the reading as to how full the tank is. I believe ford was pretty consistent through the years as to being the same Ohm range (not %100 sure on this for how many years) so if your aftermarket gauge is for a Ford sending unit it should be OK.
There is a good write up here http://www.fordification.com/fuel-sending-units.htm that helps explain it better.