hi guys , hope someone can help us. My boy friend and i have a question we took off original meter on tank got rid of all the lights and gauges want to hook up just an LED light to fuel level switch so when fuel level low LED will come on. we understand the level sensor in tank runs from full at 13 ohms to empty about 130 ohms how can we hook up LED to the sensor to make this happen. we would appreicate the help. thanks again guys.

I would just run with out a light. With the reserve on the Roadie, just run 'er till she coughs then switch to reserve and find a gas station you should be able to go at least 40-50miles before you run completely out.

If you are set on having a light, I would just trace out the wire that controlled the light on the original dash and hook a led to it and see if it works. I know there are only 2 wires that come from the tank, but, I don't think they have any power.

Steven

Thanks for the input but have already tried those two wires from harness to tank. the ones to the tank they are just leads from the float switch ( we get an ohms reading at full at 13 ohms and empty 130 ohms ) which in turn run the large harness that attached to meter assembly on tank.Our problem is there no voltage on those wires we are sure we have to introduce a voltage some where in that path but tried every thing. all other wires are accounted for except for one, the red with which says it for speed and fuel, 12 volts all time bike on or off. What's confusing is the the black from float switch run to ground so how can you run voltage through it anyway also when full seems to be the least amount of resistance 13 ohms when empty seems to be the most resistance. Well off to work any and all input would be great appreciated. have a great day guys

Depending on which color led. depends on what voltage it will need to turn on, some need 3v, some 2.5v, too much voltage and it will fry the LED, the issue you have it that at the higher resistance is when the light tuns on, which in this case lowers the volts across a ckt. All this what is needed circuit wise is in the speedo board. you would need some type circuit that senses a voltage drop because of increasing resistance, that would turn on an electronic switch that would supply the lower voltage to turn the LED on. Since the bike is approx supplying 14vdc, the circuit would need to be able to shunt the extra voltage, so the output of the electronic switch only supplies the needed voltage to turn on the LED. It's just not gonna be a cut and dry thing.

usually just a resistor with the LED is enough to cut the voltage down to the supply voltage needed, but this float level board increases resistance as the gas level decreases, hence the need for a circuit that senses all this

erbman your a sweet heart,

I'm searching for some answers, my electronic theory hasn't been used in quite some time, and if ya know that old saying "use it, or lose it" well, I've lost it! lol but we'll see what comes with some inquiries. Best I can do for now

Also checking with local electronic shop again thank you i knew someone here would know something

got this link
http://www.westol.com/~beaurega/gas.htm

hmm, might have to cut and paste, for some reason won't make it a full lik

forget the light and the gauge, open cap, look in!

takehikes wrote:
forget the light and the gauge, open cap, look in!

or like they do at the gas stations, have that huge long ruler they dip in the tank to get a inch measurement. lol I think in this case a 12 inch ruler would work.