The Ford Barn

hueyhoolihan · 06-01-2026, 10:03 PM

there are only two or three ways gasoline levels are registered. as mentioned previously, the sending unit and the gauge must be compatible. old sending units from the 40's vary the current with a rheostat in the sending unit. the gauge for those types heat a coil with a bimetallic strip attached to the arm in the gauge. modern units have nothing in common with those types. if you're using an original type of gauge it's highly unlikely a modern sending unit will work.

addressing compatibility, if indeed those are the circumstances here, would be my focus.

to test your gauge, i would simply send some current through it using a battery (possibly a 1.5v battery would suffice), so as to heat it's coil and so. bend the bimetallic strip inside and the needle. but first so as to not waste time, i would check if for continuity. a working gauge should have continuity.

if the gauge has no continuity, or if the sending unit has no continuity, or if the wire running from the gauge to the sending unit has no continuity or the sending unit is not grounded, the gauge should read empty. if there is a short in the circuit AFTER it leaves the gauge it could create a fire, but most probably the gauge would read full (this may have been mentioned in a previous post).

06-01-2026, 10:03 PM	#15
hueyhoolihan Senior Member Join Date: Dec 2024 Location: central coast california Posts: 593	Re: Fuel guage question there are only two or three ways gasoline levels are registered. as mentioned previously, the sending unit and the gauge must be compatible. old sending units from the 40's vary the current with a rheostat in the sending unit. the gauge for those types heat a coil with a bimetallic strip attached to the arm in the gauge. modern units have nothing in common with those types. if you're using an original type of gauge it's highly unlikely a modern sending unit will work. addressing compatibility, if indeed those are the circumstances here, would be my focus. to test your gauge, i would simply send some current through it using a battery (possibly a 1.5v battery would suffice), so as to heat it's coil and so. bend the bimetallic strip inside and the needle. but first so as to not waste time, i would check if for continuity. a working gauge should have continuity. if the gauge has no continuity, or if the sending unit has no continuity, or if the wire running from the gauge to the sending unit has no continuity or the sending unit is not grounded, the gauge should read empty. if there is a short in the circuit AFTER it leaves the gauge it could create a fire, but most probably the gauge would read full (this may have been mentioned in a previous post).