Fuel gauge
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Possible causes: bad sender (apparently not your problem); bad wiring/ground for sender; bad connections on wiring/ground to sender; break in the signal wire running to the gauge; bad wiring/ground at gauge; bad connections to wiring/ground for gauge; no 12 vdc power getting to gauge; defective gauge.
Note: Always test the wiring, connections, and power/ground sources before replacing components. Rule out the simple stuff, then test the components. Replace only the defective ones.
You should be able to test the gauge/wiring/connections by removing the signal wire from the sender, then turn ignition to ON [engine OFF]. With signal wire not touching anything, the gauge should swing full-scale one direction; when the sender wire is touched to electrical ground [one that actually links with the - battery line], the needle should swing full-scale the other direction. If all that works back to the end of the signal line at the fuel tank, then your problem has to be a defective ground wire/connection at the tank or a defective sending unit [even if it is 'new'].
Note: Always test the wiring, connections, and power/ground sources before replacing components. Rule out the simple stuff, then test the components. Replace only the defective ones.
You should be able to test the gauge/wiring/connections by removing the signal wire from the sender, then turn ignition to ON [engine OFF]. With signal wire not touching anything, the gauge should swing full-scale one direction; when the sender wire is touched to electrical ground [one that actually links with the - battery line], the needle should swing full-scale the other direction. If all that works back to the end of the signal line at the fuel tank, then your problem has to be a defective ground wire/connection at the tank or a defective sending unit [even if it is 'new'].
Melting Slicks
Joined: Mar 2009
Posts: 3,126
Likes: 15
I can tell you why mine did a similar thing. There is a resistor on the back of the gauge that was not making contact through itself to the contacts of the gauge. I am not sure if your '74 is even close to my '77 but looking at Willcox's info for your car is where I would start. Maybe start a new thread for this new problem. mike...
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