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Fschiesari
Joined: 05 Feb 2022 Posts: 4 Location: Italy
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Posted: Mon Aug 22, 2022 10:52 pm Post subject: Yb9 sr - reserve fuel light issue |
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Dears,
The reserve fuel light does not work, even during motor starting?
Can anybody suggest me what I have to check?
Many thanks for your help!
Fabio |
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Anders

Joined: 05 May 2009 Posts: 122 Location: Norway
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Posted: Tue Aug 23, 2022 7:01 am Post subject: Re: Yb9 sr - reserve fuel light issue |
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Fschiesari wrote: |
Dears,
The reserve fuel light does not work, even during motor starting?
Can anybody suggest me what I have to check?
Many thanks for your help!
Fabio |
I don't know about the YB9, but I guess it's a similar design as my bb1.
If it is:
The sensor in the tank may go bad. The cables inside the tank may break from vibrations.
I suggest you try to take the sensor out of the tank and take a look at it. It is a thin metal pipe with a reed relay inside. There is a float riding up and down the same pipe containing a magnet that will trig the reed relay when fuel level goes down.
You can use an ohmmeter to check for contact. It should be open when the float is at one end of the thin pipe, closed when it is at the other. _________________ Anders
bb1, Mille S2, Guzzi / Watsonian, Morini Corsaro 125, EC200, RD350YPVS etc |
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Fschiesari
Joined: 05 Feb 2022 Posts: 4 Location: Italy
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Posted: Thu Aug 25, 2022 10:14 pm Post subject: Update |
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I checked the sensor and with some fuel i have almost 1,1k ohm.
My understanding is that this resistance will change, but it cannot become 0 otherwise it will be like the switch on-off res.
I checked the cables up to the electronic board. Also the circuit of the bulb seems ok.
Any suggestion?
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Basket Caser
Joined: 22 Dec 2013 Posts: 10 Location: New Zealand
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Posted: Thu Jul 18, 2024 9:31 pm Post subject: |
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1.1 k ohm sounds about right at approximately 20 degrees C
This is a NTC thermistor which heats up with the current flow via the indicator lamp.
Kept cool by the fuel surrounding it, the resistance is high enough for the lamp to not light.
In free air, current flow causes resistance to drop and lamp will light.
Check bulb and the switched 12 volts.
Reserve switch fires the fuel pump and current flow through the lamp. _________________ When they said it could not be done, I went ahead and did it anyway! |
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