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Hi guys,

I need some advice from you all concerning my low fuel light sensor... Just came back from the 9/11 ride out east and we were running tank to tank on the way back... Since most of my buddies were on 1800's, they needed gas before I did, but I never saw my low fuel light come on...

So today I pulled the fuel pump and checked the sensor (thermistor)... The Honda manual says something like .9K ohms to 1.3 K ohms and I'm reading 1.7K ohms as measured with my Fluke Model 87 True RMS DVM...

The low fuel light does come on, but very dimly, and the gas gauge at that point is way below the red line and nearly pinned on the empty peg... OK, so all that is fine if you know your gauge and what you have left in the tank, but in regards to the thermistor, what is the common mode of failure on these???

Is it high resistance like I was seeing or do they electrically open or mechanically crumble??? Just looking for a bit of guidance here as I am thinking about ordering a thermistor and replacing it, as it appears to be out of spec which coincidentally causes a very dim low fuel light because of the increased resistance...

I would appreciate your thoughts on this matter...

Les
 

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They normally fail open -- 1.7K isn't too bad if it was about 75*F or cooler out.

You can also change the bulb in the dash (it ages faster than the thermistor) and replacing with a #168 bulb isn't a bad thing (a bit more current draw than OEM).

Thermistor can be replaced as a componant (about $5 form an electronics supply store) or as OEM equivalent (several posts on the forum).

If the bulb lights, I'd go the faster route of working the dash lamp (or all of the dash lamps while you're there) and see how it goes for you.

From the factory, the "fuel gauge" really only reacts to the top 3.5 4.5 gallons in the 6.5gallon tank -- sot hat behavior is normal. You can lengthen the float-rod to read the full 6 gallons or bend it if you like watching the bottom of the tank more than the top of the tank...

I'm not a huge fan of "running to the light" for fuel since the far more expensive fuel pump relies on fuel for proper cooling and lubrication... I'm more of a fan of keeping th pump buried well below fuel levels ;).
 

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As satan said check the bulb in the dash, if it's been changed to an LED or a lower wattage bulb there will not be enough current to heat the thermistor.
 

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dadztoy wrote:
Hi guys,

I need some advice from you all concerning my low fuel light sensor... Just came back from the 9/11 ride out east and we were running tank to tank on the way back... Since most of my buddies were on 1800's, they needed gas before I did, but I never saw my low fuel light come on...

..

Les
You must have an exceptional 1500, most 1800s get a good bit better fuel mileage then the average 1500.
 

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Thanks guys, I did order the OEM thermistor assy and will install it when it comes in... It was probably about 60 degrees outside when I checked the resistance...

Yeah, I know the fuel gauges themselves are pretty inaccurate and it's been a looooong time since I ran it down to the low fuel light coming on - I'm pretty conservative on things like that but I was riding with my group so I tried to do what everyone else was doing...

The guys on the 1800's were averaging around 35-37 but some were pulling trailers and riding two up... I don't know what an 1800 gets for mileage solo but I typically will average in the low 40's when running under 65 MPH, a bit less when running 70-75 like we were on the trip... On the one or two mileage checks I took on the trip I was right around 39.5 MPG at speeds of 70-75 MPH riding sole and no trailer...

Thanks for all the responses :)

Les
 

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Thanks to Satan for bringing up the fact that the fuel pump relies on fuel for cooling - I forgot about that... Another good reason not to ride down to the low fuel light coming on ;)

Les
 

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I changed might a couple of months ago. I light was VERY dim (when it worked at all). After I changed it, The light was just as bright as when you first turn the key on. Did you test the light by grounding the (I believe) the blue/white wire on top of the tank?
 

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The light is pretty bright with the ignition on before starting but I will keep the bulb idea in mind...

Thanks for that...

Les
 
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