MY72BUG
Hello VW world:   I brought my car out of storage today, fired it up and was faced with an old, minor but annoying problem.  With a full tank of gas my gauge never reads over 3/4 full.  Does anybody know if there is any " adjustability " on the old factory gauges or does the solution lay in replacing the fuel tank sender unit?  Has anyone faced this problem?   MY 72 BUG
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.
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hugh

I have that exact problem. I've changed the gadget on the back of the guage with several others, have tried adjusting the fuel sending unit by

bending it,replaced that unit after I ruined it and I still only get a 3/4 reading at full. If you find the answer please post it.

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MY72BUG
My current project involves the steering and front suspension but I will eventually get into surgery on this problem some time this summer.  I do have a few ideas involving the quality of the electrical ground from the tank to the chassis and from the sender unit to the tank.  If worse comes to worse, I have a complete spare tank in my loft and will attempt a wholesale exchange.  If this fails the problem must be in the gauge.  I will post the results of my work.  Dan ( MY 72 BUG ) in Goderich.
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.
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MY72BUG
OK VW world - As promised I am getting back to you about the fuel gauge problem.  First; forget about what I was going on about the quality of grounds and grounds between the tank and the chassis.  The sender unit has one wire going to it ( the one closest to the driver's side of the car ) which is a dedicated ground which goes up to the back of the gauge housing. The other wire goes to the back of the gauge itself - at least on my '72 it does.  I checked the fuse and the fuse was way too high amperage.  I put in a lower amp fuse and --- no difference.  Hmmm.  The two pieces of wiring were old and rather crispy.  Perhaps here.  Replaced them with nice new ones and new solderless terminals.  Better fit but no difference.  I switched the wires on the sender unit and the gauge shot up past full - not good on half a tank of gas.  But at least I knew that the gauge would go that high under the right circumstances.  Next stop the sender unit.  Loosening it is a walk in the park.  Use a punch and hammer to hit one of the indentations on the collar of the sender.  It does a bit of a turn and out comes the sender.  You have to wiggle and turn the unit to extract the two floats.  The long-armed float is designed to " lift " the short armed float as it rises.  The short armed float was the secret to the whole arrangement.  As it moves up with the rising float, a small contact moves up a progressively shorter series of very fine electrical contacts.  Due to some sort of resistance, the very shortest contacts at the top cause the gauge needle to move progressively higher.  The long ones at the bottom do the opposite.  There is a metal " flap " which stops the upward progress of the short arm.  Mine stopped the arm about 3/4 of the way up!  By doing some very subtle bends on this flap and a corresponding slight bend on the short float I was able to have my gauge rise to exactly the full mark.  It was handy to make the adjustments and test it without returning it to the tank.  Just raising the arm simulated a rising level of gas.  Two or three adjustments got it just right.  The hardest part of the job was getting the long float to return to the  tank without bending the living crap out of it.  The way to do this is to point the long float arm to the driver's side of the car.  A bit of deft bending gets it the rest of the way.  Oh yeah.  While you have the sender out, clean the 34 years of deposits off of the moving and fixed electrical contacts.  Mine started out dull grey but with a bit of ultra fine 600 grit  paper and some spray electrical contact cleaner, they shone like new.  As a result of this bit of work, the needle on the gauge fairly zooms up whereas before it was a leisurely movement indeed - like the hour hand on a clock.  So there you have it.  That recalcitrant fuel gauge can be corrected and other than persuading the long arm float to return to its place, the job is not so bad.  Dan ( MY 72 BUG ) in Goderich.  
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.
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