Archaeology expedition - or WTF is inside a fuel level sensor, anyway?

[gjscott]

No it is too much to pay for a dumba$$ engineered device, when a mechanical float switch would perform the same function. This another example of a solution to a problem that did not exist.

A float system without some kind of electronic dampener would be crappy too. They should use a thermistor transducer like the Japanese bikes do.

[Dry Martini]

They should use a thermistor transducer like the Japanese bikes do.

Whatever. I bet it does not cost $150.

[Bill in OKC]

I can see at least one difference between the circuit card traces and your schematic.  The 8pin IC has pin 8 (bottom right leg) going to +V and pin 4 (top left leg) going to ground.  I am assuming the white wire is + and the black wire is -.  It looks like the transistor is an open collector with the bulb tied to +V.  Your schematic should have the bulb between +V and the collector.

[scaramanga]

I'm very surprised that they don't use sensors(capacitive proximity switches) on the outside of the new plastic tanks. Very easy to do, safer and would last forever.

[Chris888]

Known dead fuel sensor gave up it's carcass for science.
This is a carbie unit, for whatever that's worth.

....

Hi, I am a new member, joined this board mostly because of this thread.
I'm having trouble with the fuel sensor on my 2002 ST4s, it reads OK when the tank is full but goes randomly to empty after about 70 miles.
I wondered if anyone on here had a good understanding of the way these things work?
E.g. what are the signals on the two wires?
what are the levels for full/empty?
Is it simply an analogue current drawn proportional to fuel level or is it more complex?
I am slightly hampered with workshop space at the moment, but I am an electronics designer by trade, I'm also reluctant to throw money at replacing unreliable parts with the same.
I also can't just pull the bike apart and work it out from scratch, as I commute on it most days, so any headstart I can blag is going to be welcome!
Ideally I'd also like the gauge to tell me more usefully how little is left in the tank, not go to zero when there's still about a gallon left!
I seem to always get jobs where I have a choice of pushing the tank range or filling up every day.

Cheers,
Chris