erratic petrol gauge.

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TRM-TUNING
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Mon Feb 09, 2009 8:01 pm

filled the car up last night all was fine. drove to work this morning and noticed gauge was reading empty. when i stop at junction's it moves like crazy almost with the engine rpm. there is still a full tank in tho.
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TRM-TUNING
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Mon Feb 09, 2009 10:15 pm

just reading through old threads is there a nut on the back of the gauge that needs tightening.
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ChemicalAl
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Mon Feb 09, 2009 10:24 pm

Yep - either that or you need new SI Batteries.
1987 E28 528i Diamond Black 74k
1986 E28 525e Saturn Blau 72k
1988 E28 525i 56k
1987 E28 525e 51k
1991 E32 730i SE Granite Silber 75k
1988 E30 316 Black 81k
1992 E30 318i Touring Diamond Black 43k
1990 E30 325i Touring Alpine White 2 65k
1986 E30
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TRM-TUNING
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Mon Feb 09, 2009 10:55 pm

ChemicalAl wrote:Yep - either that or you need new SI Batteries.
wot are SI batteries
:?
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ChemicalAl
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Tue Feb 10, 2009 8:56 am

If all the service indicator (SI) lights on your car work (all green, yellow, red) then I suspect that your batteries are fine, if not you'll need to change them:


If you take the clock cluster out (which you'll need to do to tighten the wee nut on the back of the fuel gauge anyway), then undo the screws on the back and then carefully take out the circuit board at the bottom, you'll see two rechargable nicad AA batteries that power parts of the cluster including the fuel/temp gauges and SI lights.

These batteries are soldered into the board, so you'll need to source spare batteries and a soldering iron (Maplins) and then get to work de-soldering and re-soldering.

I need to do this to mine, but i've never soldered a thing in my life and an scared i'd feck it up! Good luck doing yours (if it needs it).

One other thing, if your cluster needs a front fog indicator light, its obviously advisable to fit this whilst you have the cluster out.
1987 E28 528i Diamond Black 74k
1986 E28 525e Saturn Blau 72k
1988 E28 525i 56k
1987 E28 525e 51k
1991 E32 730i SE Granite Silber 75k
1988 E30 316 Black 81k
1992 E30 318i Touring Diamond Black 43k
1990 E30 325i Touring Alpine White 2 65k
1986 E30
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TRM-TUNING
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Wed Feb 11, 2009 6:45 pm

nuts tight but still same prob gonna do batteries at the weekend.
:x
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ChemicalAl
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Wed Feb 11, 2009 8:50 pm

lets know how you get on
1987 E28 528i Diamond Black 74k
1986 E28 525e Saturn Blau 72k
1988 E28 525i 56k
1987 E28 525e 51k
1991 E32 730i SE Granite Silber 75k
1988 E30 316 Black 81k
1992 E30 318i Touring Diamond Black 43k
1990 E30 325i Touring Alpine White 2 65k
1986 E30
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badassyas
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Wed Feb 11, 2009 11:37 pm

had the exact same problem, take your rear seat base off, remove the inspection plates. the passenger side float was buggered on mine so you can try that first. unplug it, see what happens. shouldnt be erratic... then get a wire and bridge the plug. i think you ought to get a full tank of fuel reading. with nothing being erratic, if it still is. plug it back in. and try the otherside. hope this helps....
Rav335uk
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Thu Feb 12, 2009 12:19 am

as he said, mine was jumping allover the place and turned out to be a buggered fuel sender too.
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