Fuel gauge stopped working

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CooterS
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Fuel gauge stopped working

Post by CooterS »

Hello,

New to scooters and having a blast! Just ran into a problem with gas gauge. Parked it one day working fine, now won't register. Took off the handle bar cover to look but didn't see a fuse or any loose wires.

Ideas on when to start my trouble shooting?

Thanks
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Remous
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Post by Remous »

Is your speedometer not working as well? I just had this problem, the one wire underneath the instrument panel came loose and wasn't attached.
CooterS
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Post by CooterS »

Remous wrote:Is your speedometer not working as well? I just had this problem, the one wire underneath the instrument panel came loose and wasn't attached.
speedometer is working, although I think it registers the speed a bit optimistically :lol:

I looked for loose wires and didn't see anything, but since the previous owner removed the hang down front turn signals I will admit the 4 unplugged wires meant for the signal lights distracted me.

Just so I'm clear - your loose wire fixed your issue, if so I'll get back in there to check it out again.
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Remous
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Post by Remous »

Actually now I can't remember if my gas gauge was off as well but I know for sure my speedometer and mileage ticker was not moving. I don't think the cable that I had screwed back on would have had anything to do with the gas gauge :?
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babblefish
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Post by babblefish »

Put some gas in the tank...?:)

The fuel gauge is a pretty simple circuit to troubleshoot because there are only two wires involved: a black ground wire and a black w/white stripe wire which carries the actual feedback voltage from the float/sensor sender (in the fuel tank) to the gauge. There are no fuses involved here.

So, there is one of four things that could be the cause of the problem:
1) The ground wire is disconnected from chassis ground.
2) The black/white signal wire is either disconnected or grounded due to a break in the insulation and contact of the bare wire to the chassis.
3) The fuel gauge is faulty or the needle is stuck. Light tapping on the gauge with the key in the "ON" position might free it if it's stuck.
4) The float/sensor sender unit in the fuel tank is faulty.

If it turns out that the fuel level sender is the problem, it may be possible to repair it if you feel comfortable removing it from the fuel tank (simple, just four screws). Looking at photo #2, you can see the wiper and the contacts on the board. Sometimes those contacts get coated with residue from the fuel (especially if cheap gas is always used), thereby causing an insulating layer of film which prevents the wiper fingers from making electrical contact with the board. Clean the contacts on the board by wiping lightly with a Scotchbrite pad or very fine (600-800) grit wet-dry sandpaper. You might even get good results with an ink-pen eraser. Wipe off the contacts with a solvent such as alcohol, carburetor cleaner, or brake cleaner.
BTW: The photos are of the fuel level sender from my Blur, but the Buddy's should be very similar.

As a side note, if your fuel gauge never seems to read "Full" even after a fill-up, then there's a good chance the float level contact for the "Full" signal is oxidized and needs cleaning. The reason for this is because this particular contact spends most of it's life exposed to open air (because your tank is never always full) allowing oxidation of the contact to occur.

Good luck with your repair.
Attachments
Close-up of wiper and contacts.
Close-up of wiper and contacts.
fuelsender2.jpg (31.9 KiB) Viewed 1457 times
Sender unit removed from tank.
Sender unit removed from tank.
fuelsender1.jpg (39.73 KiB) Viewed 1457 times
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goodalle
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Okay, got a resistance meter out...

Post by goodalle »

Babblefish: Trying to use my brain here: I took out the gas float unit. I disconnected and measured the resistance. These are not lab conditions, but there was a definite resistance gradient around 1.1 KOhm when the float pushed down for empty and going to close to 0 KOhm when the foat pulled up to stimulate tank full. So, I'm guessing the gauge is a voltmeter and that the float unit lever operates a rheostat type resistor.

It didn't measure such large differences when I measured it the same resistance at the speedo end. In fact, I can't be sure if there were predictable differences.

If I'm right, and there's a fair amount of if there, then the unit would seem to be operational.

Am I on the right track?

The speedo is working and all other functions do seem good.
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babblefish
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Re: Okay, got a resistance meter out...

Post by babblefish »

goodalle wrote:Babblefish: Trying to use my brain here: I took out the gas float unit. I disconnected and measured the resistance. These are not lab conditions, but there was a definite resistance gradient around 1.1 KOhm when the float pushed down for empty and going to close to 0 KOhm when the foat pulled up to stimulate tank full. So, I'm guessing the gauge is a voltmeter and that the float unit lever operates a rheostat type resistor.

It didn't measure such large differences when I measured it the same resistance at the speedo end. In fact, I can't be sure if there were predictable differences.

If I'm right, and there's a fair amount of if there, then the unit would seem to be operational.

Am I on the right track?

The speedo is working and all other functions do seem good.
Yes, you are exactly right about the function of the fuel level components. If you are seeing totally different readings between the float rheostat and the connection at the fuel gauge, then I would ohm out each individual wire for a bad connection or high resistance due to a corroded wire. Keep in mind that a wire can look perfectly fine on the outside (the insulation), but be corroded and disintegrating on the inside. Pay particular attention to the crimped connection at each electrical connector. Btw, you are taking ohm readings at the fuel gauge end with the gauge disconnected, right? Otherwise, you may get erroneous readings because the fuel gauge electrics will be in parallel to the sender.
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JettaKnight
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Post by JettaKnight »

Remous wrote:Is your speedometer not working as well? I just had this problem, the one wire underneath the instrument panel came loose and wasn't attached.
Huh? The gas gauge is electric, the speedometer is driven by a rotating cable.
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bingetv
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Post by bingetv »

I know this is a year-old thread, but I'm stuck. I have a non-functioning gas gauge. Pulled apart the scooter to get to the sender unit. It seems to have tested fine. When I put a meter across the leads on the speedometer, it reads a certain amount of resistance (something like .35 ohms). When I move the sender unit by hand the resistance changes from 0 to .45ish directly connected to the amount of movement). Seems to work, since the tank is about 1/6 full at the moment, which would explain the .35 number.

So, seems that the resistance measurement is getting all the way to the leads connected to the speedometer. Next step is to take apart the speedo unit, which I have not been able to do. I can't figure out how to remove the little needle assemblies, which need to come off for me to remove the plate with the printed numbers/logo/etc.

Any suggestions? Do I have to replace the whole speedo? Seems like it might be a waste of $89 since I'm not confident that it will fix the problem. Note also that I've had some electrical issues recently (fuse near battery keeps popping - I think it might be a short in the left-front signal light).

any help is much appreciated. thx.
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JettaKnight
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Post by JettaKnight »

Check your numbers - .35 Ohms is really, really small. My guess is you mean .35 kiloOhms, i.e. 350 Ohms.


And if you verified the sender and the cable, then it must be the gauge. Did you verify you get 12V at the gauge?
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bingetv
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Post by bingetv »

JettaKnight wrote:Check your numbers - .35 Ohms is really, really small. My guess is you mean .35 kiloOhms, i.e. 350 Ohms.


And if you verified the sender and the cable, then it must be the gauge. Did you verify you get 12V at the gauge?
I ordered a new speedometer unit and the gauge works perfectly. Not sure what went wrong, but it's working now. Thanks!
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