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LPG gauge stuck
http://lpgforum.co.uk/viewtopic.php?f=28&t=14270
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Author:  agostino [ Thu Jul 06, 2017 12:37 pm ]
Post subject:  LPG gauge stuck

Hi All,
i realised my LPG led gauge is stuck on full, even with the empty tank.
It used to fix itself over time before, but now looks like it is not going to budge.
Any suggestions?
thanks

Author:  hitman [ Thu Jul 06, 2017 12:46 pm ]
Post subject:  Re: LPG gauge stuck

yes - forget about it , just zero your tripmeter every time you fill up , you'll get to know when you need to fill by mileage ticking over.

mines been bust for ages , but its given me the benefit of getting a full tank of gas when filling up , float obviously goosed.

I know safety blah blah blah

Author:  Brian_H [ Thu Jul 06, 2017 9:03 pm ]
Post subject:  Re: LPG gauge stuck

Might be worth a look at the sender if you can get to it - Depends where the valve is on the tank as to if thats an easy task or not. Depends if its the sender itself (likely as its exposed and electrical) or the float. You can test it with a multimeter and something metal to move the sender if you can remove it (its magnetic so a screwdriver on the back should work ok).

Don't think its likely to be the wiring as they usually drop down voltage as the level drops, so a broken wire should give an empty reading. Could be a short though.

Author:  LPGC [ Fri Jul 07, 2017 9:52 am ]
Post subject:  Re: LPG gauge stuck

Bri's advice is sound, it is most likely to be a broken sender, though it could be wiring.

The most common types of senders are 0-90ohm, close to 0 ohms when empty and close to 90ohms when full, if this type of sender is fitted and there is more than 90ohms across it (including if it's broken or not connected) the gauge will show full all the time... could be wiring. This type of sender forms the pull-down side of a voltage divider circuit, no pull-down side to the divider circuit and the divider circuit outputs the full 5v (which is input voltage to the divider circuit). The ECU probably expects above about 2.3v to mean a full tank, because the 90ohm of the sender pulling the 5v down to 0v is balanced by more than 90 ohms pulling the voltage up, so even with a good sender connected and giving 90ohms the divider won't quite output half of 5v.

The next most common type is 50ohm senders, on most setups these work the other way around so a short would have gauge show full tank and open circuit show empty tank.

If the gauge moved in the wrong direction it could point to incorrect settings in software (setting 50ohm instead of 90 ohm or vice/versa).

Spec of the sender might be written on it (and 1090 or 1050 would point to 90/50 ohm respectively).

Vertical toroidal tanks are an exception, the gauge on them might show clockwise position for empty tank and anticlockwise for full tank (moves in the opposite direction)... but special senders are available where resistance rises/falls in the opposite direction to match the opposite direction of the gauge!

Simon

Author:  agostino [ Fri Jul 07, 2017 10:29 am ]
Post subject:  Re: LPG gauge stuck

Alright thanks everybody.
My gauge is visible by removing the cover of the toroid tank. At the moment it reads 1/2 and the gauge reads full.
I did remove the wiring and used some contact cleaner and now it reads 3/4.
Using the king software it appears my sender is set as nonstd.
I will play a bit with the numbers there till I read correct :)
Doesn't seem like rocket science.
Worst case scenario I will get a new gauge dial (its fixed by two tiny screws)

Author:  agostino [ Fri Jul 07, 2017 2:29 pm ]
Post subject:  Re: LPG gauge stuck

ok looks now its working properly now
thank you for the idea of using the screwdriver to turn the dial and be able to calibrate correctly
I saw the sensor is somewhat "simple" inside..I guess oxide will overtime form and prevent proper measurements...
looks like a dud design

Author:  LPGC [ Sat Jul 08, 2017 9:43 am ]
Post subject:  Re: LPG gauge stuck

In King software 'None standard' is the same as 0-90, just that it allows the installer to adjust how many switch fuel level LEDs light up for a given voltage from the sender / divider circuit. 'None standard inverted' allows the same for 50ohm senders.

Some senders use a variable resistor so can give continuously variable resistance the full range of float movement, others use resistors so have a set number of different resistance values over the range of float movement. Different types have different pros and cons including in terms of reliability when somewhat open to the elements.

Author:  Oldskool [ Wed Jul 26, 2017 9:38 am ]
Post subject:  Re: LPG gauge stuck

Contact cleaner for the win :D

Author:  agostino [ Wed Jul 26, 2017 12:17 pm ]
Post subject:  Re: LPG gauge stuck

The gauge contacts are sealed inside the transparent body and not accessible...
I used a dremel to drill a small hole and spray the contacts with contact cleaner.
It did work, now I have a reading at startup.
After driving out instead the reading is always full...
probably the contacts are dud now...

Author:  Brian_H [ Wed Jul 26, 2017 7:47 pm ]
Post subject:  Re: LPG gauge stuck

agostino wrote:
The gauge contacts are sealed inside the transparent body and not accessible...
I used a dremel to drill a small hole and spray the contacts with contact cleaner.
It did work, now I have a reading at startup.
After driving out instead the reading is always full...
probably the contacts are dud now...


Might well be - but a replacement gauge isn't a lot of money, fairly easy to swap if you can remove the screws from the old one and the wiring is ok.

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