Classic/Antique Car Repair: 1955 chevy p/u, j c whitney, volt system

Question
QUESTION: I have a 55 chevy pu that's been restored. They put a 350 engine in it with automatic transmission. My question is, I just purchased a fuel gauge for a 12 volt system, which is what the mech. I took it to recommended. He pulled the sending unit out of the tank and said it was a 12 volt system and that the old guage was probably a 6 volt so that's what I ordered. I put the guage in today and it worked fine. It showed I had a little over a 1/4 tank. The problem is, I went and filled it up today after I put the guage in and now the guage is gone. It went way past everything. How do I get it to read right? Do you fill it up and try to bend the guage or what? I didn't get any instructions with the guage so I just put it in and hooked it up. I don't know if there's something that needs to be adjusted or what needs to be done. Any help is appreciated.
Ronnie


ANSWER: Ok, lets try to sort this one out. I believe that the 55 Chevy pick up was originally a 6 volt system. If I read your question right it is now a 12 volt system. If I am wrong let me know. If you are using the original gage then you will need to put a resistor in the voltage feed line to the gage. These are available from places like J. C. Whitney.
Brad

---------- FOLLOW-UP ----------

QUESTION: No, it's not the original gauge, it's one I ordered from Chevyduty.com. What I ordered was a 12 volt gauge, but since they don't stamp anything on the gauge, I don't know if it was or not. If I get a resistor, where do I put it? Right before the gauge or around the sending unit? Can I get a resistor at an auto parts store? Thanks for the quick response on the previous question.
Ronnie

Answer
Ronnie, one thing that I should have mention before is to make sure that the wire between the dash gage and the tank sender is not grounded anywhere. If this wire is grounded it will give an over full reading. Also make sure that the fuel tank float did not get caught on something holding it full. The resistor goes in the line before the dash gage. Again Hemmings Motor News, what I consider the bible for parts for old cars, will list some one that sells them in the classified section. Try Hemmings on line and see if it is there.
Brad