Anybody ever measured the ohms on the yellow fuel level wire when the low fuel lamp circuit white wire gets continuity to ground?

I have an annoying K75S where the idiot light comes on when there's two gallons left so I want to adjust it to come on with five liters left like it's supposed to.

duck wrote:Anybody ever measured the ohms on the yellow fuel level wire when the low fuel lamp circuit white wire gets continuity to ground?

I have an annoying K75S where the idiot light comes on when there's two gallons left so I want to adjust it to come on with five liters left like it's supposed to.

I found it started to flash after using 13 litres. Constant on after using about 14 litres. On my K100RS I have managed to run the tank down to take over 20 litres without running out.

I would do a refuel when it comes on and see how much it takes.

If nobody knows then my plan is to carry a multimeter in a bike where the light comes on at the "right" time and then pull over right away to measure the yellow wire ohms.

Then when I have the "bad" fuel level sender on the bench I can adjust the little gear wheel so that the low fuel wire triggers at the same resistance of the yellow wire as the good one.

I seem to recall that RBM has written up and posted in a thread here a procedure for calibrating the fuel level sender and the low fuel light.  I think it was about 2-3 years ago.

Point-Seven-five wrote:I seem to recall that RBM has written up and posted in a thread here a procedure for calibrating the fuel level sender and the low fuel light.  I think it was about 2-3 years ago.

Already checked that thread and it's not there, just the max and min ohms.

I'm lazy and had that same annoying light so I just bent the float arm. It now comes on with 3-4 quarts left, 30 to 50 miles till empty.

duck wrote:If nobody knows then my plan is to carry a multimeter in a bike where the light comes on at the "right" time and then pull over right away to measure the yellow wire ohms.

Then when I have the "bad" fuel level sender on the bench I can adjust the little gear wheel so that the low fuel wire triggers at the same resistance of the yellow wire as the good one.

The ohm range seems only part of the equation; the angle and flexibility of the float wire could be the other. Considering the likely variability of the float wire's angle among senders depending upon whether the wire was made at the start of the work week or its end, the level of worker sobriety and attention given to its bend angle, the calibration of the machine bending it, the flexibility of the wire in each production run, and the effect of immersion in fuel for years on its flexibility. caveman's strategy seems to be the way to go.  I, too, was a Brick wire bender when the time came, but manipulating the sender's gear wheel still has a mysterious attraction to me. thanks to robmack.   In a way, it's unfortunate just bending it worked so well.

In 2012 Inge wrote that the range was 3.5Ω to 110Ω but indicated he hadn't verified it because he had better things to do.    I'm looking forward to your results. 

There's very little flexibility in the float "wire." It's pretty hard steel and bending it by hand, even out of the tank, would take quite a bit of force.

They were produced in a quality controlled manufacturing environment so the bend angles are very consistent from unit to unit. They are not one-offs built in somebody's garage.

Any variations between units would be caused by corrosion and wear.

FYI: I measured a fuel level sender (late version) the other day  and the range was 3-108 ohms.

RBM's very informative mother of all fuel level sender threads shows readings pf 2.3-114 ohms.

I'll add to this thread as I obtain more data.

duck wrote:There's very little flexibility in the float "wire." It's pretty hard steel and bending it by hand, even out of the tank, would take quite a bit of force.

They were produced in a quality controlled manufacturing environment so the bend angles are very consistent from unit to unit. They are not one-offs built in somebody's garage.

Consider bumping up your dumbbell workout regimen and also using needle nose pliers.

The Chevy Vega was built in a "quality-controlled environment," too.

The Vega? You could not have chosen a worse example of quality control. Chevy Vegas were crap due to multiple engineering issues and, as a low end car, GM sought to build them as inexpensively as possible.  Not to mention that quality control among US auto makers in 1970 was simply horrible and didn't improve until later when they started employing William Deming's statistical approach to quality control in order to be able to compete with Japanese reliability.

Do you think that the rest of your K bike is also built like a Vega or just the fuel level sender?

The FLS arm is difficult to bend because it is hardened (probably  tempered) steel. It's really not a good idea to attempt to bend tempered steel like the rod that holds the FLS ping pong ball. Since the steel is tempered is not very ductile and can break. Have you ever broken a cutting knife? It will bend some but at a certain point it just snaps before bending any more.. It MAY be possible to permanently bend the FLS float arm a little if you're careful but I choose not to test that theory and needlessly destroy a $350 part.

duck wrote:It MAY be possible to permanently bend the FLS float arm a little if you're careful but I choose not to test that theory and needlessly destroy a $350 part.

It IS possible to bend it; both caveman and I—and who knows how many others—have overcome BMW's space-age, highly-tempered, SWAT door entry ram-quality, steel float arm to effect the tiny change needed to give us what we thought we wanted. In my case, there was no damage to this expensive component probably because of the highly-sensitive fine motor skills I've developed in chainsaw operation. caveman must have similar hard-won ability.

As far as lessons from W. Edwards Deming go, Toyota was listening, but GM must have been talking in class and checking its Facebook pages because it led the manufacturer pack with 671 separate recalls from January 2000 to July 2022, according to the folks at BANKRATE. By now it's probably wholly-owned by the PRC.

Nonetheless, you'll likely be gratified to know that I fully support your research.

Good to know that it can be bent.

Could be easiest solution for low fuel light on a K w/o a fuel gauge.