fuel light on after draining the tank - how do I force it to comply?

[kecup]

Hi, I feel bad for annoying this forum with stupid technical questions but can not help it. My tank was removed for painting for some two weeks and after putting everything back together the fuel light just stays on regardless of the amount of fuel in the tank. How does that thing work and how do I fix it? Can the sender stuck (from being dry for 2 weeks) and will just tapping on it fix it? Or should I get a new sender? I should add the bike is 1997 1100i Sport and I have replaced the fuel idiot light with orange led attached directly to the wires that once powered the bulb.

 

k.

[gstallons]

Don't get too excited yet. Ride a few hundred miles before you decide to replace the sensor.

[twhitaker]

If it is the float type like the one on my '96 California chances are the float is stuck along the inside of the tank where the tank necks over the frame. You can carefully bend the tube away a little bit to gain some clearance. It's also possible the float is stuck on the pin because some grime got in the gap.

[Dan M]

Checking the wiring diagram (that is a V11 diagram) it looks to be a mechanical switch. Of course it is an eyetalyun diagram so some interpretation is needed. It shows three mechanical switches for warning lights, one for oil pressure, one for neutral and one for oil level. Since there is no oil level warning lamp I'll assume they meant fuel level. Anyway, the thing probably got stuck after it dried out. You can remove it and clean it with carb spray or it probably will loosen up on it's own. (another job for Seafoam!) From the diagram it closes to ground and complete the circuit, illuminating the light. You may want to lift the tank and make sure the wire is not pinched grounding the circuit.

One more thing, an LED takes very little current to illuminate. I wonder if enough ground it getting to it through the sensor to illuminate it. You can verify by checking the circuit with a test light and see if it lights that.

 

Edit: When are you going to post pics of the new paint?

[kecup]

Checking the wiring diagram (that is a V11 diagram) it looks to be a mechanical switch. Of course it is an eyetalyun diagram so some interpretation is needed. It shows three mechanical switches for warning lights, one for oil pressure, one for neutral and one for oil level. Since there is no oil level warning lamp I'll assume they meant fuel level. Anyway, the thing probably got stuck after it dried out. You can remove it and clean it with carb spray or it probably will loosen up on it's own. (another job for Seafoam!) From the diagram it closes to ground and complete the circuit, illuminating the light. You may want to lift the tank and make sure the wire is not pinched grounding the circuit.

One more thing, an LED takes very little current to illuminate. I wonder if enough ground it getting to it through the sensor to illuminate it. You can verify by checking the circuit with a test light and see if it lights that.

 

Edit: When are you going to post pics of the new paint?

 

 

Thank for help, I think similar about this. The sender looks like mechanical switch on paper but very similar to thermistor-type that MG Cycle sells (although not listed for 1997 Sport only for up to 1996 and Corsa, that is before and after my Sporti's year:) If this is thermistore kind that can not stuck, the chance is that the current is sends when tank is full is not enough to light the 2W original bulb but plenty to light up a led that needs much less juice. I do not know much about electricity but I guess I can tune the circuit with a small potentiometer to find a position where the current is just not enough to light the led when the tank is full. If the sensor is mechanical I'll just keep tapping. Will drain the tank and give it a check over the weekend I hope. I will photograph the bike after I have all that Moto Special instrument installed proper - hopefully next week.

[luhbo]

Put the bulb back in and it will work again. Or put in an apropriate resistor parallel to the led and it will work also. Basically this sensor works pretty much the same like an indicator relais. At least on my bike. It's an european version. Don't know what they sold into your part of the world

 

Hubert

[Greg Field]

The thermistor on an '04 is on the fuel-pump assembly. They're not that expensive. I have one in stock if your normal parts source does not.

[kecup]

Put the bulb back in and it will work again. Or put in an apropriate resistor parallel to the led and it will work also. Basically this sensor works pretty much the same like an indicator relais. At least on my bike. It's an european version. Don't know what they sold into your part of the world

 

Hubert

 

Pity is I do not know what the appropriate resistor should be. Will give it some time on weekend.

 

kecup

[kecup]

The thermistor on an '04 is on the fuel-pump assembly. They're not that expensive. I have one in stock if your normal parts source does not.

 

Will it fit on 1997 1100i sport?

[luhbo]

Pity is I do not know what the appropriate resistor should be. Will give it some time on weekend.

 

kecup

 

Google for Ohms Law. 75Ohm/2Watt might do. But be carefull, electronics is not my business.

 

Hubert

 

PS: don't buy the thermistor. The problem is the LED.

 

Edit: on third and fourth thought I think it's more complicated even. A bulb is a thermistor/varistor itself, you can't replace it in this case by just putting in a standard resistor parallel to the LED.

Edited August 1, 2009 by luhbo

[John Neeson]

Hi, I feel bad for annoying this forum with stupid technical questions but can not help it. My tank was removed for painting for some two weeks and after putting everything back together the fuel light just stays on regardless of the amount of fuel in the tank. How does that thing work and how do I fix it? Can the sender stuck (from being dry for 2 weeks) and will just tapping on it fix it? Or should I get a new sender? I should add the bike is 1997 1100i Sport and I have replaced the fuel idiot light with orange led attached directly to the wires that once powered the bulb.

 

k.

 

 

You need a resistor in series with your LED. The voltage across the LED is around 2V - look at the the datasheet for your LED to find the exact value.

That means your resistor has to drop the remaining 10V. Choose a value suitable for the current that the LED requires - again see the datasheet.

For example if your LED needs 20mA, then the resistance = V/I = 10V/20mA = 500 ohms. I think that the nearest preferred value is 470 ohms, which is close enough.