Anyone with original '40 fuel sending unit?

[sjaakslinger]

Is there anyone here who is running the original heating coil type fuel sending unit and gauge?

Just wanted to know if it's normal for the needle to wobble a bit around it's position...

Dennis

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[mcgarrett]

I am using the original 1940 Ford fuel gauge and sending unit. Both seem to be working properly without any wobbling or wavering of the needle. Check the surface where the screws attach the sender to the tank and make sure the area is clean and no corrosion on the screws.

[Kube]

No wobbling on any of them.

[deuce_roadster]

If your sender is toast, ALL the 6v King Seeley (1936 to when they went to 12v) fuel sending units are the same, only the float arm is different. You can switch to another known good one and make the arm match the arm on your 40 unit. There are 2 little metal stop tabs that control how far the arm swings up and down too.
As others have said, if you pop the cap off an clean the points that might be all it needs but be careful of the small hair like wire.

[sjaakslinger]

Thanks everyone. I did open up the sending unit. Took the mechanism out and sanded the points. I hooked it up to the original gauge and the indications were off.

I adjusted it with the toothed wheel in the sending unit and in general the indications are ok now.

Only thing is the slight wobbling. It seems to run a current, then the gauge reaches the correct position, then the current drops, then needle drops just a little bit, current runs again, etc., etc.

I'll see if I can upload the video. Either here or YouTube.

Dennis

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[sjaakslinger]

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https://youtu.be/JiRN6M3mOvY?si=W6IcXHRnwsoKXvQ4

Might be a bit hard to see, but at some positions the needle can be seen unsteady.

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[glennpm]

J Seery provided a great article discussing, "How Ford Gauges Work"

In this thread, https://www.fordbarn.com/forum/showt...Work&showall=1

Also starting on page #96 of the Techno pdf linked in my signature below.

"When the ignition switch is on, current flows through the circuit and warms the Sending Unit bimetal by means of a heating coil, causing the bimetal strip to bend and open a set of contact points. When the points open, the current is interrupted allowing the bimetal to cool and close the contact points again. This cycle then repeats and the points vibrate open and closed pulsing the current in the circuit.

Because the current through the heating coil in the Sending Unit also flows through the heating coil in the Gauge Unit, the amount of heat supplied to the gauge unit is about the same as the heat in the Sending Unit. The amount of heat in both units is controlled by the average current flowing through the circuit due to the repeated opening and closing of the contact points."

[19Fordy]

Run a ground wire from one of the gas tank sending unit screws to the frame and see if they will help. That's what I did to make sure the gas tank sending unit is really grounded.