Fuel Sender - how does it work?

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Fuel Sender - how does it work?

Postby jpsmit » Sat Jul 17, 2021 3:22 pm

and how can I check.

I am about to turn my attention to the Fuel Tank on the GT. Of course the original sender is dead and unobtanium. However, an MG Midget sender fits. I have a vague troubling thought however that it works opposite to the Vauxhall sender and thus would read full when empty and vice versa.

Can anyone shed light on this? Including how I might check - I do have a multimeter.

thanks all!

JP
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Re: Fuel Sender - how does it work?

Postby droopsnoot » Sat Jul 17, 2021 6:01 pm

The fuel tank sender is a variable resistance, or rheostat, which provides a variable resistance to earth, similar to how the temperature gauge does, albeit in a different way. You have 12v on one side of the gauge, and the sender varies the earth by moving the rheostat "pointer" on the coil inside the sender body as the float moves up and down. At maximum fuel height, the resistance will be at its minimum and allow the gauge to read high. At minimum height, the resistance will be maximum and give a lower reading. Basically it's a voltmeter, and the sender varies the reading by altering the earth.

To test it, read the resistance from the body to the terminal with the float at either end of the scale. I don't know the resistance range on a HB sender - I'm not sure I remember it for HC, for that matter.
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Re: Fuel Sender - how does it work?

Postby brading » Sun Jul 18, 2021 6:29 pm

This shows you how to check a fuel sender unit. https://www.youtube.com/watch?v=9YgPeM2dpcE

The HA fuel range is Zero ohms empty and 30 ohms full

Its not just the variation in low to high and high to low there are variation in those also such as 0 to30 and 40 to 250
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Re: Fuel Sender - how does it work?

Postby jpsmit » Mon Jul 19, 2021 2:06 am

this is very helpful - thanks! anyone know the range for HB's (GTs)
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Re: Fuel Sender - how does it work?

Postby brading » Tue Aug 03, 2021 5:51 pm

Follow the diagram below then you will know what range sender you need.
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Re: Fuel Sender - how does it work?

Postby jpsmit » Wed Aug 04, 2021 1:08 am

awesome - thanks - no just need the energy to get out and play with it!
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Re: Fuel Sender - how does it work?

Postby brading » Wed Aug 04, 2021 7:06 pm

I take it you know how to find the ohms readings for the sender. If not with the sender out of the tank connect your multimeter on ohm's between the sender to gauge terminal and the sender body, then take a reading when the float is at the bottom of the stroke and again when the float is at the top of the stroke. Oh Dear something to do with my age just noticed that I had posted about checking the sender ohm's.
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