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Fuel Guage reads backwards?
Can I just reverse the wires coming off of the pigtail from the fuel tank to make the fuel guage go Up when I add gas as opposed to going down when I add fuel?
Ren Man |
Nope. Resistance is resistance no matter which way you measure it! You probably have a gauge that is not matched to the year of your sending unit.
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What gauge mfr. and part number are you using and what sending unit do you have in your tank. I had the same problem with a SW gauge and a GM sender. I ordered the correct gauge and the problem was solved. SW makes three different gauges for Ford, GM, and their own sender (0 to 240). If I'm not mistaken, Ford changed their gauges a few years ago creating problems between years for the FFR guys. I have a number for SW US if that's what you have. DO NOT start crossing wires. It is a gas tank you are messing with, afterall.
Gary |
There is no power so to speak going to the fuel tank but I guess I need a different sending unit?
I'm using a match set of Ford Motorsport Guages and have a late model mustang fuel tank. Wonder if Ford would be able to tell me of a different sending unit? There has to be a way to change the resistance of the sending unit??? |
Somewhere around 1989, Ford changed the resistance of the sending units. The earlier ones were 73 ohms empty, and about 10 ohms full. The newer ones are 16 ohms empty, and 158 ohms full. You can pull the sender out of the tank and easily check it w/ a DVM. Or, fill the tank and check it in place. You'll probably have to get w/ the Ford Motorsport guys to verify the gage. Then you have a choice, change the gage or change the sender, whichever is easiest and/or cheapest. Good luck! :cool:
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The new sending units that Ford Motorsport uses is 240 Ohm empty and 33 Ohm Full. So, I'll check to see if I can get a sending unit.
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Just by looking at it totally electrical:
the resistance could be changed by using resistors in line or parallel. i.e. two 100 Ohm resistors in para result in 50 Ohm total. one 100 Ohm and a 50 Ohm in para result in 100+50 / 2 = 75 Ohm. Two 100 Ohm in line - you guessed it: 200 Ohm total. Matching it exactly through the hole range is a real challenge ... Dominik |
Sorry Dominik
Resistors in Parallel:
With resistances in parallel, the total resistance is less than that of the lowest resistance value present. The correct formula would therefore be: . 1 _________________________ . 1 1 1 . ____ + ___ + ____ . R1 R2 R3 Two equal value resistors is parallel will be half the value as you stated in your example above. - Jim - Note, just reviewed my answer and see the formula came out distorted. It should read the reciprocal of the resistors values added together and then dividing the sum into the number one. |
This is how I fixed this problem. I actually bent the float bar in the opposite direction. Period. Original sending unit reads correctly and in the proper direction now.
Thanks everyone. |
Good save, I admire your ingenuity...Bill
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Jim,
thanks. Has been a while since school, but it's never too late for corrections. |
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