So having issues with my 1950 Chevy 3100. Got it running (mostly), and last nagging issue is the fuel gauge already read EMPTY. Reviewing this thread I did some testing at the sending unit, underneath the cab. After cleaning grounds, and cleaning the sending unit connector... now the fuel gauge reads FULL (I mean slammed completely to the right). Disconnecting the sending unit wire, nor grounding the gauge wire at the sending unit connector has any effect on the fuel gauge reading FULL (doesn't even flick when connecting or grounding). At one point I accidentally connected the sending unit wire with the ignition switch on... which also seems to be when the fuel gauge went from reading EMPTY to now reading FULL. Switch on or off makes no difference in the results though (before or now).
QUESTION: Does this mean I somehow burnt out the gauge ? I would expect a burn-out gauge to go to its resting state, not full power state (although, see below, my thinking on operation may be backwards).
I have determined that at least the sending unit itself seems to be bad as it still reads ZERO Ohms with a half-full tank. That will be replaced tomorrow probably, but Phak1's trouble-shooting steps in this thread do not seem correct to me looking at the electric schematic for the 3100. If others have found this to be correct, then obviously I'm wrong, but maybe someone could point out my error to help me finalize my trouble-shooting.
1) 12V from the battery (6v in my case via an inline resistor at some point) goes via ignition switch to one side of the fuel gauge.
2) Other side of the fuel gauge goes to the sending unit
3) Other side of the sending unit goes to ground.
4) I assume the fuel gauge reads EMPTY when no power, meaning that is its resting state (i.e. NO POWER = EMPTY on gauge)
5) That would mean maximum voltage to the gauge would translate into maximum deflection of the gauge (i.e FULL on gauge).
6) An empty tank however would provide maximum resistance translating to minimum voltage to the gauge (i.e. EMPTY on gauge).
The trouble-shooting write-up however has the gauge indicating FULL with no power (i.e. "At the sending unit, remove the wire that goes to the gauge"). And likewise when you ground the wire feeding the gauge at the sending unit... it is suppose to read empty (although that is completing the power circuit and so should be providing maximum voltage and deflection of the gauge (i.e. FULL).
Like I said, obviously I'm mistaken in my thinking... but the only way I can see trouble-shooting steps being correct is if the OFF resting state of the gauge shows FULL... which seems unlikely. Since it hasn't worked since I got the truck though, I really am not sure.
Kudos to the first one that shows me the error in my thinking :-)
Thanks... Joe
