Anyone who has read the diagnostic section of their factory service manual has come across the mention of "Tool C3826" or "C3826A." This is the tool that has three settings- "E", "1/2" and "F" and is used to test the dash gauges in many years of Mopar cars and trucks. I can't find a source for these tools, but reading the FSM leads me to believe that this tool is basically a three position variable resistor- "E" would be maximum resistance, indicating an empty gas tank, "1/2" would be 1/2 resistance, and "F" would be little or no resistance, indicating a full gas tank.

I think it would be fairly simple to create one of these at home using simple components from Radio Shack (a three position toggle switch, some leads, some resistors, and a box), but the magic question would be the value of the resistors.

Anybody own a tool C3826 or know what the resistor values should be? Would it be safe to get some ohm readings from a known good fuel tank sending unit and use these as the resistor values for E, F, and 1/2? It seems this would work since my 83 van service manual says you can substitute a fuel sending unit for tool C3826 in testing the fuel gauge if the special tool is not available. The same tool is also used to test the temp gauge and oil pressure gauge, so the same values as provided by the fuel sending unit should be correct for all gauges, yes?

8-10 ohms "full" ,75 ohms empty

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V8?? We don't need no stink'n V8!!

Ahh, thanks! I might make building one of these a back burner project. On the other hand, I suppose one could just use a fuel level sending unit for all tests instead of building a tool from scratch.

I tested my sending unit on my workbench and I'm getting about 7ohms FULL and 70ohms EMPTY. The question: Is this an accurate test while the sending unit is out of the tank and on my bench?

Some years ago, I made up my own testing tool w/ power resistors, a little plastic box, and some bananna plugs from Radio Shack; works fine.

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obliquely-inclined state of mind

Sweet. That is exactly what I was thinking of. I knew somebody had to have done this before!

I suggest that link become a sticky in the electrical forum.

I took all the info at the A body site & complied it into 1 annotated diagram assuming a sticky would rather pull up the gut info:
https://picasaweb.google.com/1079134575 ... 5205329426

I believe my 65 Dart has the voltage limiter built into a guage so verifying whether the limiter is effecting the results or the guage itself might be an added step?

My guage shows "overfill" when the tank is filled and shows 1/8 when I'm down only 6 gallons......with a new sending unit of questionable quality.....so this test might tell me if the new sending unit is not spot on?

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1965 Dart 110k, 225, Carter BBD Super Six, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. throwout bearing, HEI, electric fan, ram air/heated air, Accusump. http://plymouthcarclub.com/