1963 Gas Gauge

[Jerry Coia]

How do I test my fuel gauge? Mine reads 1/2 full.

Thanks.

Jerry

 

[JohnZ]

Quick-Check: For the “quick-check”, remove the (brown or tan) gauge wire from its “S” terminal on the sending unit, use a jumper wire to ground the connector, and turn the key on – the fuel gauge should peg to “Full”; then disconnect the light green (63), black/pink (64-65) or pink (66-67) power wire connector from the “I” terminal on the sender and use the jumper wire from the connector on the tan wire to the connector on the power wire, and the gauge should peg to “Empty”. If this occurs, the problem is in the sending unit, not in the gauge; if your results are different, the problem is in the gauge or the wiring to the gauge.

Full System Check: The step-by-step full system check is as follows;

• Check the dash gauge power terminal (light green-63, black/pink 64-65 or pink 66-67 wire) at the gauge connector to ground with the key on (with the multimeter set for “volts”, not with a test light) to verify that you have 12 volts to the gauge.

• Check the power wire connector terminal (light green-63, black/pink 64-65, or pink 66-67) at the sending unit to ground in the same manner with the key on to verify that you have 12 volts to the sending unit (this terminal is marked “I”, for “ignition”, on original sending units).

• Same check as the “quick-check” outlined earlier.

• Remove the black plastic ground connector from the spade on the sending unit and use the multimeter (set on “ohms”) to check from that wire connector to a known good ground on the frame; you should show zero ohms (no resistance). If you don’t, there’s a problem in that ground circuit, which runs forward through the body harness and the multiple body connector above the driver’s side kickpad where it connects to the instrument panel harness. That wire finally grounds through the black pigtail that that comes out of the 3-cavity radio connector and screws to the bottom of the dash cross-brace with a star washer to the left of the radio; this one point grounds EVERYTHING at the rear of the car, including the dome light, and grounds the cluster as well.

• If everything checks OK to this point, it’s time to check the sending unit. With the key “off”, disconnect all three wires at the sender, and connect the multimeter (set on “ohms”) to the two pin terminals on the sender (power and gauge terminals). Have a helper with small hands or a wooden stick with a hook in the end work the float up and down slowly in the tank, and the multimeter should read zero ohms with the float all the way down (empty), and 90 ohms with the float all the way up (full), with a smooth, linear progression between the extremes. Now connect the multimeter to the gauge pin terminal (marked “S”, for “sender”, on original sending units) and to the ground spade, and repeat the float arm movement; you should see the reverse of the first test, with zero ohms with the float all the way up (full) and 90 ohms with the float all the way down (empty). This verifies that both sides of the voltage divider circuit are working properly. This same routine can be used to bench-check a sending unit before installing it in the tank.

 

[Jerry Coia]

John,

Thanks for such detail. I'll try it and let you know how I make out.

Thanks again,

Jerry