?? Low Fuel Indicator Light ?? A Challenge for the RSV Experts...

[foyerboy]

So many of you guys have a lot more mechanical wisdom than I do so I am posting this question for your opinions.....

 

I recently went completely through my bike getting it restored (99RSV), new paint, new parts, new mods, blah blah, blah- you get the point. When we reinstalled the gas tank getting everything put back together the low fuel indicator light now stays on. The contacts appear to be good and I cleaned them for good measure(where they connect in front of the tank), still the light stays on. This morning I replaced the fuel thingy in the tank.....still same problem. Now though here's what happens:

Turn key on, get correct fuel level reading on gauge momentarily then all fuel bars blink 7 times pause, blink 8 times pause, blink 8 times again, then only the top fuel bar continues to blink(the bar for totally full) none of the other bars light, meanwhile the low fuel indicator remains lit.

 

The tank has about 5 gallons of gas in it. One more thing I will include is that I replaced all my indicator lights in the dash with LEDs which take much less wattage to operate are a lot brighter and have a long long life.

 

What are your thoughts ??

 

:detective:

[rickardracing]

Take the led's out and put stock oones back in and see what happens.

[foyerboy]

Yeah, trying to avoid that as a last ditch effort.

[Guest tx2sturgis]

I'm not an 'RSV expert' but my guess is that the LEDs are causing an issue, either with the lack of load, the resistance, or the fact that the circuit may be designed to send a signal THRU a regular bulb, and the LEDs wont pass that signal. LEDs are diodes and they block reverse current flow.

 

Just a guess.

 

And besides, the amount of wattage that the original incandescent bulbs used is not enough to worry about, and as far as brightness...I would not want them glaring in my face at night.

 

Yes, its a pain changing them all back to original, but I'm betting it will fix the issue. If not, then you probably still have a problem with the sending unit.

 

 

 

 

[PGunn]

Quick test would be to make a quick harness plug it into the the tank sending unit using the old (orginal) gauges and lights. This would save ripping everything out and woulod allow you to test different resistors on the leds to figure out what is going on.

[rickardracing]

I agree with Brian. The led's are the "major" non-stock change. By-pass those somehow OR change back to stock, problem just may go away.

[LilBeaver]

This sounds like a fault code to me folks. Check the service manual Page 8-82.

 

Service manual says either the sender unit or the fuel thermistor.

[foyerboy]

Rick,

Isn't the Fuel Thermistor part of the sender assembly I just replaced inside the tank? What are the odds of a brand new fuel sender assembly in the tank being bad?

[PGunn]

If what Foyerboy is saying is correct then I would look at the resistance of the sending unit. Think of it as a volume control (variable resistance) now if the new gauge unit (LEDs) operate at one resistance and the OEM gauge set operates at another their is your mismatch. One way to check it is use an Ohm meter and very the sending unit between full and empty then check the manufactures of the LED set and see what the operating resistance is suppose to be. You solution may be as simple as a road trip to your local Radio Shack and pick up a resistor to put between the sending unit and the LED gauge set to match what is called for.

[LilBeaver]

Rick,

Isn't the Fuel Thermistor part of the sender assembly I just replaced inside the tank? What are the odds of a brand new fuel sender assembly in the tank being bad?

 

Well, the chances of having a new one be bad is pretty slim [provided by NEW you mean it was brand new from the factory], BUT you are getting the code. Further testing of the fuel sending unit is really pretty straight forward; PGunn mentioned this already.

 

If what Foyerboy is saying is correct then I would look at the resistance of the sending unit. Think of it as a volume control (variable resistance) now if the new gauge unit (LEDs) operate at one resistance and the OEM gauge set operates at another their is your mismatch. One way to check it is use an Ohm meter and very the sending unit between full and empty then check the manufactures of the LED set and see what the operating resistance is suppose to be. You solution may be as simple as a road trip to your local Radio Shack and pick up a resistor to put between the sending unit and the LED gauge set to match what is called for.

 

A preliminary test of the fuel sending unit can be completed without removing the tank. All you need to do is take off the black 'ignition cover' thing that surrounds where you put your key in near the fuel filler cap. The wire harness on the left [clutch side] of the tank underneath that cover. This wire harness has 3 wires in it. One of them is the ground, one is for the fuel 'level' and one is for the thermistor [what triggers the fuel light and fuel trip meter]. These ARE on separate circuits. As indicated, the fuel level circuit will have various resistances for each level that the fuel registers at (it is not a potentiometer [variable resistor] but each level has a distinct resistance that will change as the float moves inside the tank). The thermistor [low fuel light & fuel trip meter] is not as complicated. It is a simple 'continuity' or 'no continuity' type reading. The thermistor and ground wires should be the green/white and black, respectively.

 

If that all checks out okay [again, like PGunny said] then you can replace the low fuel light bulb with the original bulb to see if the problem goes away or put a resistor of the equivalent spec, in line [thereby defeating the power savings of the LED] and see if that does it.

 

After close inspection of the electrical diagram, it does appear that the thermistor runs in series through the low fuel light bulb -- but I question that accuracy since if something happened to that bulb the trip meter would then not be function properly -- at any rate, your problem is pretty much one of a few things, as identified:

1) Fuel sending unit/thermistor

2) LED bulb throwing off the system

 

Sorry, I guess I should not have responded last night when I was so tired as I did not really think through the issue as carefully as I should have before writing it out.

 

Hope this is helpful.

[Guest tx2sturgis]

 

1) Fuel sending unit/thermistor

2) LED bulb throwing off the system

 

 

If you reverse those, thats what *I* said!

 

[LilBeaver]

If you reverse those, thats what *I* said!

 

 

Did someone hear something? *crickets chirp* Hmmm, I guess not.

 

:moon:

 

For what it is worth, I did say:

[...] your problem is pretty much one of a few things, as identified [...]

:rasberry:

[Guest tx2sturgis]

Did someone hear something? *crickets chirp* Hmmm, I guess not.

 

:moon:

 

For what it is worth, I did say:

 

:rasberry:

 

Thats not crickets...thats a TURKEY!

 

[foyerboy]

Looks like I'm going to have to crack open a fairing.....Ugg!

 

[PGunn]

I would hold off on cracking the faring and try what Lil Beaver said, check the wiring under the cover.

I do have one quick question you did say you had the same issue with the sending unit you took out and it was working without an issue before the gauge swap? If so and the error is idenical as the new one if so the whole thing sounds like a resistance issue which would be the easy thing to check using the old one.

[djh3]

I rememeber reading a thread over on the Kawaski boards that was simular. In that the fellow changed out some of the indicator lights for LED. That was the bug in the system, and it had to do with the low fuel light. If the old sending unit was OK I would use it as a tester to see if you got the same thing going on. Sounds to me the 2 easiset things to do is use the old sending unit (if thats an ok spare) or change the low fuel light and see if that fixs it.

[foyerboy]

FYI everybody,

Brian (tx2sturgis) and LilBeaver were correct. WillBill1 helped me switch the low fuel indicator light back to the stock incandescent and it fixed the problem. With that being said all the other dash lights work correctly with the new LEDS installed and are brighter.....which I like. The only dash light you cannot replace with an LED is the Low Fuel light.

 

One other thing you should know if anyone does this upgrade. If you install LED's in your dash, LED's are polarized, meaning you have to put them in just right. An incandescent can be installed one way and then flipped over and it will still work fine. The LED needs to be tested to make sure it lights up before you button everything back up. If an LED does not work carefully remove it flip it around and you should be good to go.

 

Thanks again to WildBill1 in Mooresville NC for all of your help, and thanks to the others of you that helped me arrive at this conclusion!