Single Wired Fuel Sending Unit

I torn out my interior on my Transtar last night to get around to fixing the Fuel Sender and to clean the Seats and Carpeting. The gas gauge seem to work. . . When I start the truck the needle quickly moves from empty to Full and pegsout at Full and sticks. I have to rap on the glass to get it to empty again once I turn off the truck. . . it does not mover if I simple just turn the swtch to on. I will be removing the sender tonight but I really don't know what I looking for to make this unit work. . . I'm confused about a single wire going from the fuel guage to the sender and that's it. . . I have a hot wire running from my switch to the gauge and then on the other pole of the gauge it runs to the sender. I don't understand how it works from there. What I do have is another sending unit (which I hope is not bad from Lloyd truck) that I can test with . . . is there something I should know about these units?

Reply to
Rick Courtier
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The fuel sender is a variable resistance to ground; the fuel gauge basically measures how much current is flowing through the whole circuit. I believe that when you test the sending unit you should measure the resistance between the screw terminal and the body of the sender, it should match whatever the specs are for a Stewart-Warner sender (I think 33 ohms when full, 240 empty? check and make sure, this info should be available on the web) if it meets those specs and resistance varies smoothly through the whole range of travel then your problem is likely in the gauge, or the wire between the gauge and the sender. If you have a ground on the wire between the gauge and sender, that would cause it to peg all the time, so check the body harness for crimps and chafes.

Also, if you are using a 6V gauge and sender in a vehicle that's been converted to 12V, you need to either replace both the gauge and sender with 12V versions or use a "runtz" to drop the voltage. The specs I gave above are for 12V gauges only.

good luck,

nate

Reply to
N8N

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