Low fuel light question

[blupupher]

So a question on the low fuel light.
Mine does light up, both with the key check (very bright as it should be), and when the fuel is low (around a gallon of gas left, fuel gauge at the low side of the red on the fuel gauge).
The issue I am having is the light is very dim when it comes on when low. I can't see it in bright sunlight, and even on a cloudy day, can't be seen unless I look directly at it.
Is this normal (does it get brighter the lower it gets) or is my low fuel light sensor going bad?
I am usually looking for gas when it comes on, so I have never pushed it past just a few miles from it coming on (the most I have added is 5.78 gallons, and light was still dim).

[Erdeniz Umman]

It should get brighter as the fuel level drops.

[dingdong]

Yes that is normal. The sloshing fuel is still cooling the thermister.

[blupupher]

OK, was just wanting to make sure the resistor was not going bad or something.
Just seems weird that even with 1/2 gallon of fuel the light still barely visible.
Not a huge deal, as said, my gauge works, and I know my range is in the 150-170 miles if doing all highway (just need to make sure I reset the trip meter every fuel up).
I am thinking of doing an Iron Butt SS1000 this spring, and have been doing some prep rides to see how I feel (only done ~400 miles at one time so far), but getting my range figured out as well as the low fuel light is something I needed to do for sure.

[Solo So Long]

Have you made sure that the contacts were all shiny clean?

[blupupher]

I have not pulled anything apart to look since I did not know what was or was not normal.

[Solo So Long]

When you have some time, it would probably be worth pulling the instrument cluster and replacing all of the bulbs. While doing this, check each socket for voltage -- including the ground side. A low voltage will give a dim bulb, and may mean a corroded connection somewhere.

. . .and don't forget to take a look to see that the indicator lenses aren't dirty. It doesn't take much crud to make the lights seem dim.

Motorcycles are highly susceptible to corroded connections, simply because water gets sprayed onto random parts of the harness.

[blupupher]

The light is bright during the bulb check with initial key on, just never has gotten bright when it gets low on fuel, just a dim glow.

[4given]

Search “Rebuilding Replacement Low Fuel Sensor”. It’s a long post but if you want some background on the low fuel light failure and solutions to the problem you can get lots of info there.

[blupupher]

Search “Rebuilding Replacement Low Fuel Sensor”. It’s a long post but if you want some background on the low fuel light failure and solutions to the problem you can get lots of info there.

I had come across that post and read some, but I don't recall seeing anything about a dim light, just the light not working.

[4given]

If you replace the thermal sensor in the tank with a float switch the light will come on bright immediately when you reach low fuel level. A company called Innovative makes a stainless steel switch that works flawlessly. At least it does for me. I got the idea from that post.

[4given]

This is the one I used

[DenverWinger]

A bit of googling, but here's a link to the switch above.....

https://www.liquidlevel.com/product/sta ... witch-100/

There's a How-To Here on GWDocs for changing the thermister sensor to a float/reed switch sensor from some automotive brake master cylinders. The difficulty with these sensors is in finding a car model where the brake fluid level sensor float actually floats in gasoline instead of brake fluid. Specific car models from the '80's are mentioned as a source for workable sensors, but these cars are getting harder to find in the junkyards.

This sensor says "Float Specific Gravity = 0.50", so that's half the density of water. Gasoline has a specific gravity of about 0.75 depending on temperature and blend, so this should float very nicely!

"Good Find", 4given!, especially considering my low fuel sensor is failing, too.

[WingAdmin]

The topic Building a replacement GL1500 Low fuel sensor details the replacement float sensor and warning circuit that both Virgilmobile and I built.

We used the float from this item:

Amazon - Brake Master Cylinder Cap/Float

You cut the float switch free from the cap, and then fasten the float switch in place of the thermistor.

[4given]

A bit of googling, but here's a link to the switch above.....

https://www.liquidlevel.com/product/sta ... witch-100/

There's a How-To Here on GWDocs for changing the thermister sensor to a float/reed switch sensor from some automotive brake master cylinders. The difficulty with these sensors is in finding a car model where the brake fluid level sensor float actually floats in gasoline instead of brake fluid. Specific car models from the '80's are mentioned as a source for workable sensors, but these cars are getting harder to find in the junkyards.

This sensor says "Float Specific Gravity = 0.50", so that's half the density of water. Gasoline has a specific gravity of about 0.75 depending on temperature and blend, so this should float very nicely!

"Good Find", 4given!, especially considering my low fuel sensor is failing, too.

I can’t take any credit other than taking everyone else’s advice. I tried a Honda Civic float but the two I tried only lasted a few months. I’m not sure what I did wrong. I tried a Dorman first and after that one failed, I ordered one from our Local Honda dealer and that failed also. That’s when I discovered Innovation’s product. It’s been working flawlessly since I installed it 5 or 6 months ago.

[4given]

Thanks to Virgil and WingAdmin. And khspe2. These guys are all electronic geniuses compared to me. You are also in that category Denver. I should be paying for all the knowledge I glean from you guys and others on this site.

[DenverWinger]

The problems with using most Automotive brake cylinder sensors are the floats are very nearly the specific gravity of gasoline and don't float, or they slowly dissolve in gasoline. The Honda Civic sensor is probably one of those.

Scott (WingAdmin) and Virgil have found a good one, their sensors have lasted many years now. I was unaware of (or forgot about ) the availability from Amazon, I thought you had to go "Junkyarding" to find one.