1968 FJ40 fuel Gauge Sender (1 Viewer)

[ron1]

With a new fuel sender, the fuel gauge only goes to about 3/4 to 7/8 full when I articulate the float full up. The gauge follows properly when moving the float arm part way. When I set it at full down, the gauge indicates past empty.

I measured the unit resistance with two DMM's, and the resistance stays around 28 ohms float arm full up to almost full down. Full down it is open, or infinite ohms.

I am confused why the resistance doesn't change, but the gauge indicates with the float position, except not going to the full mark.

Am I missing something on the sender resistance?

I sent the vendor an email asking what a new sender resistance is.

Adding a 200 ohm resister in parallel with the sender, allows the gauge to indicate almost full, does not affect the empty indication much at all.

 

[45Dougal]

Don't worry about the resistance reading.
If you bend the arm down a bit, do you get the right range on the gauge?

 

[ron1]

45Dougal, good catch.

When you stated bending the arm, I thought that could be why the resistance went open circuit with the arm full down, and gauge dropped below E, overtraveling the sensor.

It was tricky to bend the arm close to the pivot so I did not need to modify the limit travel bracket.

Bottom line is it so close to F now and E, task complete.

Thanks for the tip.

 

[Engineer8000]

The resistance doesn't change because it is not a variable resistor.

 

[ron1]

Engineer8000,

I figured it wasn't a variable resistor as it looks different than another sender I have seen, and couldn't measure resistance.

Exactly what is the mechanism? Don't believe it is variable capacitance as the supply is DC, not AC.

 

[Engineer8000]

It is a bimetallic regulator similar to the oil pressure sender, it changed to a pot in 72 or 73 time frame

 

[ron1]

Thanks,

Had not seen that in a fuel sender before this one.

 

[Engineer8000]

some tech here

Fuel Sender 83320-35020, 69-72

This sender is different than the 73+ senders in that it has a bi-metal voltage regulator in it that makes testing it a challenge. The 73+ sender, 83320-60050 is a variable resistor that changes value with level, 120 ohm E, 17 ohm F. This is the inside of the 35020 sender: The bellows to the...

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