For some bizarre reason my fuel gauge is reading full all the time, and the light in it no longer works. Also the "Miles to Empty" on the LCD display just reads "Lo" which is kinda weird as the gauge reads full.... even when the tank is empty. Which tells me info to the Instrument unit is missing and/or erroneous.

If I move the float in the tank the gauge doesn't respond, but that only tells me what I already know, that something aint right.

Any wisdom to be imparted as to how to check the float and or gauge? I assume the float provides some kinda of resistance value feed back? if so, what range in Ohms should I be looking for across the output of the float, if indeed that is what I should be looking for......

 

HD's fuel gauge system sucks.
To my knowledge there is no diagnostic for either component and I've asked a few pros.
Most of us figure out our milage and use the trip odometer.

 

I'm away from my books but I could have sworn there was a diagnostic test for the sender in my '99 book.

 

Yeah its not the best system out there, but its what we have to work with.

Using the trip Odo at the moment isn't much better than a dodgy fuel gauge, since the 103 build I dunno what my mileage should be, add a 2 inch tank lift into it and things get more fuzzy........

 

Then work it and figure it out,, that part isn't rocket science.
When you find the easy answer besides replacing each component,,
,,Please,, let us know.
Short of looking up what you have, how you built it, and trying to find a video showing how you ride,, I'll just guess,,,,
,,you have a bigger motor and enjoy some of the throttle it gave you,, Right?
So you'll get somewhere around 35mph. Your tank lift is a function of Acute Triangle,, do the math for volume.,
aka; you pushing 120 miles on a trip(?),, start looking to top off.

 

Found my fuel gauge problem, dodgy connector on the fuel gauge wires, fixed now.

In other news... I did discover the following:

The float in the tank is a 210 ish ohm range variable resistor. 40 ish ohms up to 250 ish.

40 ohms is a full tank, I.e. float fully floated.
250 ohms is an empty tank, I.e. float not being a floaty thing at all.

The float also is on the high side of the tank when the bike is on the side stand, so dont ever expect it to be even remotely accurate in that situation.

You can measure it at the connector that splices in to the rest of the wiring inside the tank.

 

Damn dodgy connectors get me every time.