I haven't tried this, but it appears that someone on another forum has it and it work. The problem was using a modern 90 ohm gas sending unit with a stock 30 ohm gas gauge. Here is what they are saying is the solution:
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boxrodz
11-07-2006, 07:00 PM
If I'm following you correctly, you had mounted the 45 ohm resistor across the signal post and the 12V post of the fuel gauge. If so, you're not placing the resistor in parallel with the sending unit. You need to mount the resistor across the signal (sending) wire and the ground (not the 12V source). It should work in this configuration. Next time you're filling up and while monitoring the sending unit with the multimeter, place the resistor across the leads of the multimeter (basically between the sending unit wire and ground). It should read nomally between 0 and 30 ohms.
11-12-2006, 08:37 PM
SUCCESS!!!!!!! Boxrodz, you are the man! I wanted to post an excited and sincere thank you to all of those that have offered there input, ideas, resources and advice. I added a 47 ohm resistor (closest I could find to a 45 ohm resistor) to the fuel gage sending unit terminal, then grounded the other side of the resistor to the back of the gauge cluster by using one of the fuel gauge mounting screws. My truck fuel gauge now reads full with a full tank of gas!
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Link:
http://67-72chevytrucks.com/vboard/archive/index.php/t-210638.html Lee
