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Discussion Starter · #1 ·
my love of these bikes continues with my 3rd purchase of a 2012 f4rr , i am trying to sort out an issue with it right now as the low fuel light comes on after about 2 min and stays on .
i have changed out the entire fuel pump assembly and deleted the EVAP and still have this low fuel light issue ?
I do not think its the thermistor but have not been able to test old on or newer one .
A little back story previous owner installed a tidy tail and routed wires incorrectly and part of the rear of harness got melted and caused a short and blew the 15amp fuse that runs dash, tail , starter , the wiring has been sorted out at tail end of bike new 15amp fuse and bike is up and running again, but now i have low fuel light comming on after 2 min and stays on .
other than that bike is running great but i hate having this light on and like to be warned when i am running low on fuel .
can anyone help point me in a direction to fix this
if there was a short in the harness somewhere ( like there was in tail ) could this cause fuel light to come on ?
 

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The fact that the dash light does light after a period of time indicates that you have continuity between the Fuel Probe connector pin 4 and the Dah pin connector #7.
The thermistor works by the affect of a temperature change on conductivity. Temperature goes down when fuel is present above the unit and that switches on the light. i.e. Completes the circuit.
The light coming on suggests that the circuit is always complete at the thermistor....a sign of a failed thermistor.
The thermistor can be replaced and there are instructions for that in the Workshop Manual.
Font Parallel Diagram Drawing Art


Product Organism Font Screenshot Elbow
 

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Discussion Starter · #3 ·
very confused with this ? can you tell me how to test this ? in English looking at this circuit test is confusing , i understand i need a bulb , a 12volt battery , So positive wire goes where ? negative goes where and light bulb ?
I have a complete fuel tank pump assembly with thermistor i want to test it .
I already changed out this assembly with a know to be working one but still have light coming on
 

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Are you certain it is your Fuel Light coming on?
 

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very confused with this ? can you tell me how to test this ? in English looking at this circuit test is confusing , i understand i need a bulb , a 12volt battery , So positive wire goes where ? negative goes where and light bulb ?
I have a complete fuel tank pump assembly with thermistor i want to test it .
I already changed out this assembly with a know to be working one but still have light coming on
Font Material property Rectangle Parallel



Negative is the BLUE wire, terminal 3
Positive is the VIOLET wire, terminal 4
Their drawing is confusing as it shows the thermistor with reverse power when compared to the Electrical Schematic.
The Fuel Pump, which is circuit 1-2 should not come into play.
I would think you can simply create the circuit without the 1-2 connection and that should yield results.
Ed, @esq'z me , has taken one of these apart...perhaps he has insight into the circuit board that exists inside the Fuel Level device.
 

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The circuit board imbedded within the fuel pump wiring connection is a damper to delay the circuit response to fuel level changes and subsequent changes in temperature that turns on the light. A quick and dirty test is to disconnect the wire from the pump to the dash. Light goes out? circuit is complete and thermistor is bad (shorted).
The fuel pump and fuel level sensor use the same power supply. If you don't want the light to stay on simply disconnect it at the pump plug,
 

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Discussion Starter · #8 ·
does rear license plate light have any affect on low fuel light ? i have the wires for license light cut and tapped ( no light ) i did have a short with the tail end wiring but its been since sorted out minus the license plate light
 

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Nope. Different fuse. Different power scheme. Common ground.
 

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That's circuit check.
Do other "idiot lights" turn on then go off during the instrument check?
 

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So, because the manual does not show the wiring within the dash, I cannot determine the source of power for your Low Fuel Light to ignite with the four pin plug unplugged.
It implies a fault within the dash...or the dash connector near pin 7.
 

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That sounds like the fuel level sensor is failing..... but the sensor provides ground path for the meter indicator, so if you unplug the fuel pump you eliminate that ground. Light should go off.
Power is supplied to the meter and the indictor bulb is grounded by the fuel level sensor...so somewhere you have an alternative ground path for that circuit. It may be a lightly chafed wire insulation and so takes a moment for the current flow to increase enough to turn on the light..... OR,, the "check" circuitry inside the meter is shorting as it warms up.
 

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Follow the Violet wire from pin 4 on the tank connector to pin 7 on the dash connector.
 

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Discussion Starter · #18 ·
Follow the Violet wire from pin 4 on the tank connector to pin 7 on the dash connector.
Is there any other things that can be eliminated from that circuit such as starter switch ect. Was going to turn key on wait a minute till low fuel light came on then start eliminating things until light turns off , if that fails I will dig into wiring
 

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The Violet wire is a dead-end wire that runs from the four pin fuel pump connector to the dash.
As such, with the connector disconnected, it can only be energized through the dash, or through a short in a wire that runs adjacent in the wiring loom.
There is no schematic I can find that shows the Dash Wiring internal to the unit.
Older MV Manuals show the pathways internal to the dash.
 
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