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Fuel Level Switch


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To the best of my knowledge , this is a capacitive  type sensor and you don't test with a meter or the way you normally test . I replaced mine because of fuel leak and irregular operation . The terminal contact was broken on one terminal . After getting a used one with the wrong connector . I tried swapping connectors , wrong terminals & all kinds of mess , I went through about 10 wiring harnesses and found a terminal that somewhat worked . Hmmmmm . 

 I will check the old sensor by dipping it into fuel and test it & I will let you know what I find on how to test and what is a good reading . 

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The sensor is a thermistor, no capacitance at all just resistance that changes with temperature, yours read 1.4k because it was reasonably warm then you dipped it in fuel and cooled it down. I ju

Just put an ohm meter on the leads. "Some" resistance? It's ok. Naturally, open or shorted.. not so much.

To the best of my knowledge , this is a capacitive  type sensor and you don't test with a meter or the way you normally test . I replaced mine because of fuel leak and irregular operation . The termin

I just checked my old( IDK if it is good/bad) one and it checked 1.4k ohm and nothing on capacitance scale .  The resistance wet up to 1.8k after a dunk in gasoline . 0 in cap range .  INSPECT your connector terminals before doing anything .   

Yes , I got a used one but it had a different connector/terminals than the 03ish bike I was working on . I was going to change the connector/terminals to Weatherpack and couldn't find ANYTHING til I got finished w/the job . 

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The sensor is a thermistor, no capacitance at all just resistance that changes with temperature, yours read 1.4k because it was reasonably warm then you dipped it in fuel and cooled it down.

I just went through this again with a V7 owner, he took the regular speedo off snd wanted to use a 12 Volt LED in its place.

He tried using the LED directly with his sensor but of course found it was always lit.

I tried to talk him into using an incandescent like the VIIs use but he wasn't having it

Measuring the sensor on my V7 the thermistor is ~1,800 Ohms when cold (it will vary slightly depending on your fuel temperature) When the fuel drops below the sensor the V7 sensor starts to warm slowly until it's only around 90 Ohms.

You have to be really careful not to supply too much current as the sensor will just keep getting hotter and hotter until it fuses in a puff of smoke, the small lamp that the VII comes with is nicely balanced for the sensor, as the current goes up it lights and the current falls back. The V7 dash does a similar thing electronically, it limits the current to 75 milliamps.

 

I worked out that 150 Ohms was a good value to use in series with the sensor, it will pass enough current to warm it up but not enough to fuse it, the 12 Volt LED is wired in parallel with the resistor, it doesn't draw anything when the sensor is cold but is reasonably bright when the sensor warms up

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It doesn't come on a stick like the VII ones but I'm fairly sure its value is the same, it would certainly work with an in tank fuel pump. You could adapt the V7 one by carving open the stick to access the connections. I would try to avoid having to re-make the tank seal.

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Bram , search for a used unit for your bike on eBay or something similar where you live .  Read this entire thread for a good education while you're not doing anything . 

Whatever you get , make sure it has the same connector !

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14 hours ago, BramF said:

Is there any new info on a replacement for the fuel level switch?

After taking my tank apart in order to get it painted it seems as the switch has given up.

I've tried testing the fuel light by powering it directly and that lights it up nicely so I'm suspecting the fuel level switch of causing the fuel light to no longer work.


@BramF, a broken wire at the sensor is probably most common. Especially after some "handling." Resoldering the wire to the sensor base, then applying an epoxy retention blob (I'm sure there is a better technical name for that known method!) may save the day . . .

 

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18 minutes ago, docc said:


Broken wire at the sensor is probably most common. Especially after some "handling." Resoldering the wire to the sensor base, then applying an epoxy retention blob (I'm sure there is a better technical name for that known method!) may save the day . . .

 

Oh, hey: " strain relief  ! " :luigi::nerd:

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