My fuel gauge that last under-read about 10 years ago started it again. The Great Palm's book is very good on how to fix this problem, which, assuming the fuel tank sender is working OK, is caused by poor connections in the instrument cluster. This part of the book is attached to this post.
I knew that my sender was going home, so I had a new one ready. I tested the gauge using the new sender my connecting it to the sender loom, and the top position on the sender sent the gauge needle to just above the 3/4 mark. This was better than the old sender did with a full tank, but not correct.
So, this being a warm day in my parts, I first fitted the new sender to the tank, very easy, and then removed the intrument cluster. Illustrations below of the required steps. Having removed the cluster you then have to separate the white backing part from the black front part. There are 7 small pozi screws to undo and the parts separate. This allows access to the actual gauges.
Next you have to remove three pozi screws from the back of the white part of the cluster. Rather unbelieveably, These connect the flexi circuit board copper to the actual gauge, meremy by the threads of the pozi screws digging into the copper track on the gauge support plate. Here they are, just to the left of the larger multiplug hole:

There are two small spring clips that hold the gauge support plate to its slot in the front of the white part of the cluster. You can see one of them in this shot, and following that a fuzzy pic of one of them fitted, plus the voltmeter pointer that I mangled! :


Once these are off the gauge itself can be removed just by carefully pulling it out of its slot. The next two pics show the gauge and the slot it came out of. NOTE the gauge pic; you can see where the three pozi screw threads contact the copper track and also see the corrosion and dirt in the contact places:




The next shot shows the gauge tracks cleaned up:


The gauge has been refitted to its slot and the tiny spring clips that retain the gauge via its support plate have to be reinserted. The larger side goes outeside the plastic on one side and the smaller side has to be pushed between the support plate and the plastic on the other.

Refitting these clips is not easy, I used long nosed pliers and when in place, pushed the clip out of the pliers into its correct position with a flat bladed screwdriver.



Next i cleaned up the copper under the pozi connecting screws:


Wider pic of the cluster rear ready for the guage pozis to be refitted. I cleaned up all the copper tracks where they connect to the multiplug. NOTE: the copper track often peels back from its plastic backing where it goes downwards into the multiplug hole in the cluster. The best way I have found to rectify this is to place a tiny drop of superglue onto a small flat bladed screwdriver and us this to smear it onto the plastic below the copper; then hold the copper down with another not-glued small flat bladed screwdriver for 30 seconds to fix it. If not, these tracks will almost certainly get displaced when the multiplugs are refitted. I had to fix 3 tracks this way.


Finally I cleaned up all the multiplug connector terminals and refitted the cluster



I have ddone this once before and it fixed the problem and a full tank made the guage read full. I will report back if it works this time when I fill the tank!
UPDATE: Just impoverished myself filling the nearly empty tank (USA readers think $170 for 19 to 20 US gallons / 77 litres). I am very pleased to say the gauge reads right up to the full mark.

Palm's explanation of the problem and the fix, which is where I originally learned about it, is attached.

 

An awesome and v. Useful post...... thank you!......... praying I dont ever need to do it

 

This a correction to one of the diagrams that Greg posted. The numbers of the connections have been changed to match those on the wiring harness connectors, and the indicator left and right were reversed.
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I knew the EU had higher fuel prices, I didn’t realize it was that much higher. I also hope to never need this well detailed post. I’ll just continue putting a couple gallons in at a time, so I never actually know.

 

Thanks for reposting the diagram Jal, and thanks for improving it too. I have saved it and deleted my old one.

 

Bloody well done Greg.

All the Barrel Gauge cars will need this fix sooner than later.

Needs to be a sticky please Graham.

 

Sorted my instrument cluster this weekend. I have also added an extra earth wire as per Greg’s advice. An easy job and needed doing as my fuel gauge started to read a bit odd. I knew it wasn’t the sender as this was replaced not long ago. All fine now and reading correctly and steady. My connectors weren’t bad just discoloured but cleaning them all up has done the job.
Rob.

 

Thats a very timely repost link, as i am going to be digging into my cluster in the next several days to fix a couple things.

Thanks!

Doug