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Discussion Starter · #1 ·
65 Galaxie w/ new 66 tank & sending unit. Also have new guage. The 2 terminals on the sending unit. 1 - grnd & 1 - to guage. Should the grnd terminal on the sending unit be connected to the sending unit "case". On my sending unit, there is an insulating washer on the grnd ternimal. I do not see how it can work this way.
 

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Discussion Starter · #2 ·
Come on guys help me out. Anyone with a fuel sending unit laying on their workbench. Is the ground terminal grounded to the sending unit or isolated like mine? If it is isolated and is grounded only by the wire, what does it do?
 

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Normally the grd is picked up through the gas tank to frame to battery. Check with a ohm meter to confirm you have a good grd on the sending unit. If not hook a grd wire to it.
 

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The Sending unit had NO insulation from ground like you are implying.

There is a rubber O-ring, that's not an insulator, it keeps the fuel in... The Power wire is the one insulated.

The Ground nipple gets plugged into and grounded to the chassis.

If you got pics of yours put up front and back shots. We will help. Sorry I wasn't here for you earlier, I had to come up to the Island and repair my wife's Escort.
 

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Discussion Starter · #6 ·
Thanks guys for your replies. This is a tank & sending unit that I bought off E**y about 5 years ago. I verified that the pos & grnd terminals are in the proper loaction. I can read the resistor thru the pos terminal and sending unit "case". I went ahead and grounded the grn terminal to the case on the back of the sending unit. It seems to work. I don't think that you can rely on the sending unit to gas tank to frame as a good ground. Isn't that why there is a dedicated ground wire.

Thanks again.
Mark
 

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OK your setup is different than I had imagined. But the same principal exists. The tank being grounded shouldn't interfere in the operation of the gauge without a problem in the wiring somewhere.
 

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i don't have that style, but I do not believe that the sending unit and frame are grounded independently of each other, but, I do wonder about your setup there. where does the ground wire go from the plug backwards?
 

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Discussion Starter · #10 ·
The grnd wire goes straight up thru the trunk floor and is attached to the trunk floor just behind the rear seat.
 

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OK it's as I thought.

The system works exactly as I described, the power goes into the tank to the rheostat, the end of that wire on the rheostat is NOT grounded, the ground contacts from the float arm contact point that slides up and down the rheostat coil and delivers varying resistance to ground to complete the circuit to the gauge.

Remove the cover and masker sure the rheostat portion of the + wire is not touching any other part of the system that's not insulated.
 
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