1968 GTO 461 TH400 Auto
I have 1968 Pontiac that my fuel gauge (stock) is not working properly. I purchased a new sending unit and installed, but I am only getting a reading of little over ¼ tank when full. I tested the sending unit off the vehicle and get zero ohms when empty and 90 ohms when full. With sending unit hooked up at empty I get empty, but at full I get little over ¼ tank on gauge. Tested gauge by unhooking OHM (brown) wire at sending unit and gauge went to full, then grounded brown wire and it went to empty. I am now confused I have read that 90 ohm sending unit is correct for this vehicle, I also read that the resistor on the back of the gauge may be bad. Is there a way to check the gauge for proper resistance? Do I need a 30 ohm sending unit? Can you purchase resistor for this gauge and if so what resistance?