I replaced my fuel sender on my 75 L bug with a brand new Mexican one as my fuel gauge was only reading half full when full. I tested the unit with the sender out of tank and got movement from empty to full. I then put it in tank which when refilled has about 1/2 a tank. The needle only moves slightly into view.
Any ideas?

Bad earth? Try running an earth wire from the sender the body.

I had a problem with the fuel gauge on my 67 beetle not working correctly and it ended up being a bad earth connection. The earth cable end was a large round crimped connector that was connected by one of the screws used to attach the sender to the tank. Problem was, the inner diameter of the round connector was too big compared to the diameter of the screw. This meant that you could screw the connector down using the screw but it would not actually touch any metal for a good earth....once I figured out what the issue was I changed to a smaller connector and problem solved....


Regards
Greg

Problem solved. Pulled tank out for the third time. Tested everything which was fine and put it back in and all good. Thanks for the input. cheers