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Hey everyone, so I'm having a continuous issue with my fuel gauge. It wasn't working at all before, but I got it fixed. The only problem is it reads backwards and my mechanic spent countless hours trying to figure it out. He said that my gauge isn't compatible with the stock gas tank I have. I've already changed the sending unit three times (last time was because my mechanic broke it while trying to modify it). I'm trying to figure out what the solution is. When I fill up the tank, the gauge goes all the way to empty and works its way towards full as the tank empties. Part of me is thinking just let it go, since it still gives me an idea of how much gas I have in the tank. I'm just trying to see if there's an easy fix without spending more money on this issue. I'm attaching a picture of the gauge....i believe the brand is dolphin.
745218
 

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My 1st thought is that you have the power and ground terminals backwards on the gauge. If you've checked that already and they're correct, maybe they're wired wrong internally. I just went through this with elec cooling fans- the manufacturer had internally wired the harness backwards and the fans wouldn't engage.
 

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Why does my gauge read backwards?
The first step would be to make sure that you have the proper ohm range fuel sender to match your gauges. For example a 73-10 ohm fuel sender would read backwards on a 0-90 ohm fuel gauge. If you find you have the correct ohm range fuel sender make sure that the float arm is installed on the correct side. The front of the rheostat shows which side the float should stick out from. If the float arm is installed on the other side the gauge will read backwards. Also if the rheostat is installed upside down the gauge will read backwards.

 

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I looked at the Dolphin website, they don’t really show individual gauges. I’d give them a call. I know Auto meter makes different versions of the same fuel gauge, depending on whether you are using a Ford, Chrysler, GM or universal sender. Dolphin may require their sending unit.
 

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Dolphin says it's a programmable gauge, and that it includes a sender.
Not a lot of info on the site though. I'd try emailing them.
 

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It all depends on the gauge movement and the gauge-sender compatibility.

The original gauge used a resistive element to heat a bi-metal spring and move the gauge. Reversing the leads on the gauge wouldn't reverse the gauge operation at all.

The original (and reproduction replacement) sending units are a "73-0 ohm" type, where the lower the resistance the more voltage supplied to the gauge and the higher the reading. Other manufacturers (GM for instance from the mid-sixties), use a "0-90 ohm" and modern Fords use a "16-158 ohm" system. Installing a gauge made for one of these with an OE sending unit WILL result in a gauge that not only moves backward but never goes full scale.
 

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Sounds like another case of "just because it fits doesn't mean it will work". Try to find a Ford compatible gauge that looks like the one you already have.
 

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What tank sending unit are you using? Does the gauge match the tank sending unit OHMs That is, 76/6 or 76/10 OHMs. This is the first aspect to insure.
 
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