Repairing Low fuel warning light not working

[Old Rider]

King winter now starting to arrive so i have now wrapped the bike in for hibernation.The testrides showed that the fuel light worked as it should,but
when riding i also taught about the test i did earlier with water when the bulb did not shut off. It could be that i installed the thermistor not careful
enough and one of the wires got too close the metal inside the canister making a short.i have to replace the sender gasket anyway so i decided to check
the thermistor some more.After inspecting it more i found that one of the wires on the thermistor was very close to the metal wall inside and need to be
fixed.

After reading a little in the docs i linked to about explosions in gas tanks  the repair now feels very safe.
https://www.nrel.gov/docs/fy09osti/44040.pdf
https://www.nrel.gov/docs/fy10osti/47819.pdf
https://www.nrel.gov/docs/fy11osti/52043.pdf

[wco56]

Old rider, I see you had the same issue with your fuel light sensor. I have had issues with mine as well. I see this is from October of last year but thought this might be worth mentioning anyway. I ordered up the Thermistor unit (the case with the Thermistor inside) on eBay here in the US. It is for a Datsun 280ZX Thermistor Low Fuel Warning SENSOR Replacement. It looks to be exactly the same size and specs as the FJ1200. If you do have any issues with your fix you may want to locate one. I have not received it yet but I think it will do the trick unless there is something I missed.

[Pat Conlon]

Thanks for the tip Wayne, please report back when you get the unit and let us know how it works out.

Cheers

[Old Rider]

Old rider, I see you had the same issue with your fuel light sensor. I have had issues with mine as well. I see this is from October of last year but thought this might be worth mentioning anyway. I ordered up the Thermistor unit (the case with the Thermistor inside) on eBay here in the US. It is for a Datsun 280ZX Thermistor Low Fuel Warning SENSOR Replacement. It looks to be exactly the same size and specs as the FJ1200. If you do have any issues with your fix you may want to locate one. I have not received it yet but I think it will do the trick unless there is something I missed.

Hi Wayne i also found that on eBay  also found another one that has 2 wires on it. I posted 2 pics of how they look .The canister has to be welded/soldered on the fuel level sender holder arm and  the wire soldered in the sender or spliced  so it is a little work involved with that too.
Mine works fine ,but i did some more searching for a thermistor that was straight so you don't have to bend the wire inside the canister and i did find one see the pic
below. I ordered it to see if that was a better option than the thermistor i installed ,but that ended up beeing a funny story.

[wco56]

I pulled the sender unit out and had everything waiting to go when the new thermistor arrived (see attached photo). The size was exactly the same as the old part and the install was very straightforward. I did have to solder the casing into the wire mount, which was simple enough. I also cut the thermistor wire to length and soldered it in place to complete the circuit. I would say the only thing to be aware of is when you solder the wire inside the housing be sure the slack in the wire does not interfere with the sweep on the sender itself. Sorry but I was remiss in not taking photos of the new thermistor in place. I bench tested the sender unit and the thermistor to be sure it was operational and I installed with a new rubber gasket to seal it in the tank. It works fine and it doesn't get much easier than that from my perspective. I will say that when I bought the thermistor on eBay I paid $5.00 USD. After I bought mine I see the seller is asking $30.00 USD now. At $5 I got a true bargain, but at $30 I would consider Old Rider the fiscal winner, and I would seriously consider doing the extra work to make the fix.

[Old Rider]

I pulled the sender unit out and had everything waiting to go when the new thermistor arrived (see attached photo). The size was exactly the same as the old part and the install was very straightforward. I did have to solder the casing into the wire mount, which was simple enough. I also cut the thermistor wire to length and soldered it in place to complete the circuit. I would say the only thing to be aware of is when you solder the wire inside the housing be sure the slack in the wire does not interfere with the sweep on the sender itself. Sorry but I was remiss in not taking photos of the new thermistor in place. I bench tested the sender unit and the thermistor to be sure it was operational and I installed with a new rubber gasket to seal it in the tank. It works fine and it doesn't get much easier than that from my perspective. I will say that when I bought the thermistor on eBay I paid $5.00 USD. After I bought mine I see the seller is asking $30.00 USD now. At $5 I got a true bargain, but at $30 I would consider Old Rider the fiscal winner, and I would seriously consider doing the extra work to make the fix.

Great work! I'm very curious about  what type thermistor  is mounted inside .Is it the original yamaha shape or maybe it is the same type i have mounted a bead with 2 wires coming out from one side. Did you try to take a look inside the canister and did you measure the ohm resistance ?

[wco56]

Sorry, but I never opened the canister up. I didn't want to take a chance on causing damage. I didn't take readings on the resistance but I did check resistance to see if it changed when heat was applied to the canister. Everything checked out good and I installed it. I figured I will give it a real world test when spring arrives here in New York State, but that will be a couple of months from now.

[Old Rider]

Hello some of you might think (or hoping) i was dead from a gastankeksplosion ,but im not! im alive so far    I have now added a fuse and a weaker bulb to make
things more on the safe side .Since im not a expert on electronics im not sure if the fuse will do anything =) But a weaker bulb will atleast make the thermistor run cooler that i have tested.

[red]

Hello some of you might think (or hoping) i was dead from a gastankeksplosion ,but im not! im alive so far    I have now added a fuse and a weaker bulb to make things more on the safe side .Since im not a expert on electronics im not sure if the fuse will do anything =) But a weaker bulb will atleast make the thermistor run cooler that i have tested.

Old Rider,

Just a suggestion, but if you have another thermistor handy, you might want to keep what you have going there.  As a separate experiment, try using an LED bulb instead of an incandescent bulb.  They are more Off/On, and need much less power than a normal bulb.  You may need a resistor in line to reduce current flow into the LED bulb, but the LED should be brighter in-flight.

[Old Rider]

Hi Red. I have tested with a LED bulb i wrote about it in my first post .If using a LED bulb it will pop on and off too fast so i think that the bulb will light up even if there is alot of fuel in the tank when turning left or accelerating and fuel is splashing around.I will flicker.With the normal iridescent bulb it takes about 10-15 seconds for the bulb to start to glow and it light up first weak when fuel getting lower and stronger and stronger as fuel level sinks.