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If it's anything like the Aspencade there is just black paint where the symbol would be and it can be cleaned off with alcohol. Then you can add an insert to display what you want or even just use a colored bulb.
Here is an example of a similar job to add an alternator light..
So many cars have low fuel lights, that a trip to a salvage yard can probably get you some dash insert that will work for you.
 

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Discussion Starter · #22 ·
Thanks again Rambo. I decided to try to get the LED Low Fuel light that I bought to work. I found a thread about converting dash light to LED (which I haver done already). However, none of them have a thermistor in the circuit. The poster of the thread stated a 470ohm, 1/2 watt resistor was needed across the leads of the LED to make it work. I happen to have some, and tried it. The LED still lights with a full tank.
Now a stupid electrical question. I read the low fuel circuit in the manual I have, and to me it looks as if the thermistor just supplies a ground for the circuit when it warms ( I assume when it warms it closes.) My question is, the low fuel connection (tab) at the top of the fuel pump assembly is for a ground wire (I'm assuming), and 12v for the circuit comes from a switched 12v supply, correct? Or do I have this backward? I have tested continuity to ground the low fuel tab, and there is none with a full tank, however, when I connect the negative lead of the LED to it, IT LIGHTS! I don't know where the LED is getting its ground to light up. I have done a continuity check on the LED negative lead to ground, and there is none.
Now I am wondering if the low fuel tab is for a 12v supply instead of a ground.

Any takers???

TIA
 

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02 GL1800 w/Auto Pilot
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I doubt you will be able to make a LED work for the Low Fuel light.
Why bother to replace the incandescent bulb anyway?

the high current of the bulb is necessary to make the Thermistor work...

and LEDs light up pretty quick with even a very small amount of current flow.
 

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Discussion Starter · #24 ·
Hi John,

The original issue is my bike is an Interstate. No Low Fuel circuit. I was trying to add one. I thought adding a resistor to the led would make it work, but so far no. I'm still guessing if the low fuel tab out of the top of the fuel pump assembly is a ground connection for the light? Or is it for the 12v supply for the light?
John, if you don't think a LED will work, how could I wire a 194 bulb to have a low fuel indicator? Or, am I SOL?

TIA
 

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1993 GL1500 Aspy 1980 GL1100 STD
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The correct wiring is from +12v thru a 194 bulb and the ground site of the bulb to the Low Fuel thermister terminal on the fuel pump assembly. The other side of the thermister is grounded within the assembly.

The way this works is the thermister is about 2000 ohms to ground when at ambient temperature. That resistance is too high to light a 194 bulb, but will light a LED all day long. But the current flowing thru the bulb and the thermister is enough to start heating the thermister. This is a "Negative Coefficient" thermister, so when it starts heating up the resistance goes down, so you now have more current thru the bulb and thermister which causes the thermister to heat even faster. The other thing is the filament in the bulb also decreases in resistance when it heats up. Finally the resistance of the thermister is low enough, like 25 ohms, that the bulb is glowing brightly.

But when the thermister is submerged in fuel, it is prevented from heating up, resistance stays around 2000 ohms and the bulb does not light.
 
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Discussion Starter · #26 ·
The way this works is the thermister is about 2000 ohms to ground when at ambient temperature. That resistance is too high to light a 194 bulb, but will light a LED all day long. But the current flowing thru the bulb and the thermister is enough to start heating the thermister. This is a "Negative Coefficient" thermister, so when it starts heating up the resistance goes down, so you now have more current thru the bulb and thermister which causes the thermister to heat even faster. The other thing is the filament in the bulb also decreases in resistance when it heats up. Finally the resistance of the thermister is low enough, like 25 ohms, that the bulb is glowing brightly.

But when the thermister is submerged in fuel, it is prevented from heating up, resistance stays around 2000 ohms and the bulb does not light.
And this is why a LED will not work.

Ok, thanks guys. I'll have to go another route. I'm thinking this is turning into a winter project!
 

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what DenverWinger said, is precisely correct.

as your bike never had the low fuel setup, you will have to make one up.
the 1500s have the Thermistor attached to the bottom of the fuel pump bracket.
 

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Discussion Starter · #28 ·
Yeah John, I bought a OEM replacement fuel pump assembly, and all that was available was the ASP/SE one. It fits fine, and pumps as normal. I just thought it would be as easy as plugging in a light to the Low Fuel tab and I'd be fine. LOL
 

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Yeah John, I bought a OEM replacement fuel pump assembly, and all that was available was the ASP/SE one. It fits fine, and pumps as normal. I just thought it would be as easy as plugging in a light to the Low Fuel tab and I'd be fine. LOL
then you have solved the problem, mount a 194 bulb somewhere and source it to 12V accessory block.
Job 1 done. It would do fine behind the 5 amp accessory fuse, as it will only pull current when the fuel gets really low.
 
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