Low fuel light if LED always on? Ideas??

Hi all, I just switched all the gauge cluster lights to LEDs on my 03 and noticed that my low fuel warning light stays on at all times (I have a full tank), I also noticed that that particular incandescent bulb was slightly larger than all the other the warning lights, which caught my attention (turns, CEL, locker, cruise, etc are all the same, just the low fuel warning bulb as an outlier).

I put the slightly larger incandescent back in and the light went off.. the bulb is in fine shape and not burnt out, it works because it was on earlier today before I filled up.

So, I’m wondering if anyone else who has swapped ALL their gauge cluster lights to LEDs experiences this, has found an LED solution to this, or if you too had to swap that particular bulb back to incandescent ???

I’d really like to have it all LED, even if it will only be on for brief periods of time, infrequently, it’d be annoying to know that 22/23 are swapped to LED lol.

Ps. I put in an electronic flasher relay and that helped all my turn signals, since there isn’t a way to wire a resistor into the socket for the warning lights I’m wondering if there may be a fix like the electronic flasher relay, but for the cluster.. my google searches don’t take me anywhere useful

 

If it is a different sized bulb in that position, does it call for a different led? Sounds like the resistance isn't high enough in circuit. Did you try swapping it with any of the other leds that are same size?

 

That’s what it appears to be in my opinion as well. I did try swapping for another led or two from the other warning lights hoping it was just a out of spec bulb I put in, but no luck. It would appear I need to track down the difference in bulb size and try to find the appropriate LED replacement, even though they take the same socket the bulbs are clearly different.

 

Yeah, I haven't done this swap or mod before but I know many guys have on here. Maybe one will chime in for us and let us know for sure. Is the low gas indicator original bulb a different part number from the others?

 

It's a simple circuit. Thermistor in gas tank in series with low fuel warning bulb. When the thermistor is submerged in gas it stays cool and has high resistance. When you have low fuel the thermistor is above fuel level and heats up and its resistance drops allowing more current to the warning bulb.

Bottom line is the bulb and thermistor resistances need to match. When you put in an LED it has a much higher resistance and requires less current to light up, so it's lit up always. The old bulb always had current going through it but not enough to light up.

I don't know of any easy way to make an LED work in the circuit. There's no real good reason you need an LED there other than to say you have 100% LEDs installed.

 

Very well explained. I didn't know the circuit used a thermistor. Cool

 

I reckon incandescent it is then!

Thanks for the excellent, albeit dream crushing, explanation. Unless someone chimes in with an easy fix it seems to be too much trouble, I can live with 22/23

 

Same thing happened with my 2000 Taco. Thanks for the info. My battery, Cruise, and airbag lights do it too. The airbag one stays one faintly even after the truck is off. Does that make sense?