Does anyone know how the fuel sending unit works?

[hosspuller]

Easiest fix is to replace the sender, but that's a $100 gamble without sure knowledge. I would take it out, make sure the float has free movement. Dunk the tube in a container of fuel to simulate different fuel levels. Then check the resistance between the leads as the float is moved in the tube. you might find the resistance doesn't change or the float gets stuck.

Post back what you find.

 

[super55]

I agree its most likely the sending unit in the tank. They work off a rheostat so it is basically a bunch of wound wires that a contact slides against. The amount of current or in this case resistance caused by the rheostat dictates where the level will be on your fuel gauge.

 

[Industrial Toys]

Very interesting. So a reed type has numerous reed switches and the magnet on the float only activates one or maybe two at a time? How many wires go to the sender? Or is it read electronically back to the instrument panel?

True though. Old style is just a variable resistor with common ground and one lead to the gauge. Power goes to the other side of the gauge.

 

[TractorGuy]

Best refer to the service manual for your model.

Some sending units may vary a ground and some may vary current.

Either way a service manual will give the ohms variable for testing.

 

[country101]

Best refer to the service manual for your model.

Some sending units may vary a ground and some may vary current.

Either way a service manual will give the ohms variable for testing.

I don't have a service manual or even an owner's manual. I think I found which owner's manual I need for my model, but the guy at the parts counter told me a different number each time I asked after I saw things that didn't look like they went on my model. Is there a way to look these up by serial number or look at them without paying $300 for one that might not be the correct technical manual? I can access the owner's manual online, but only looking at part of a page at a time is near worthless.

 

[country101]

Very interesting. So a reed type has numerous reed switches and the magnet on the float only activates one or maybe two at a time? How many wires go to the sender? Or is it read electronically back to the instrument panel?

True though. Old style is just a variable resistor with common ground and one lead to the gauge. Power goes to the other side of the gauge.

I don't recall off hand how many go to it, but I think it might only be 2.

 

[super55]

Very interesting. So a reed type has numerous reed switches and the magnet on the float only activates one or maybe two at a time? How many wires go to the sender? Or is it read electronically back to the instrument panel?

True though. Old style is just a variable resistor with common ground and one lead to the gauge. Power goes to the other side of the gauge.

You know thats good question. All the equipment I have is the old rheostat which is easy to tell by the float attached to a long throw arm. I would think a reed switch would also work on a resistance some how to get a variable reading. Maybe the contacts are V-shape to vary the resistance. Now you got me wondering. Next time I come across one I have to cut it open and peek inside.

 

[Industrial Toys]

You could just wire each reed back to segment on an LCD graph.

You could change the parallel reed switch inputs to serial data and send them to the dash.

You could wire each reed switch to a different value resistor and mimic the old reostat.

 

[Tx Jim]

Shown below are the spec's for the fuel sender that hosspuller listed part #. Spec's shows full & empty ohm's

 

[hosspuller]

Folks ... I have miss-lead you. I wrote "reed switch" Deere only says "reed" Could have a very different meaning and operation.



Super55 ... please post what you find of the innards of such a level sensor.


Country101... I have two manuals for my 2015 Tier 4 5065e

Diagnostic TM901619
Repair TM901519