VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Gas Guage 31 Coach

Hello All,I had my tank boiled and cleaned out at local radiator shop last year and purchased a new sending unit from FS.I made certain the tank was well grounded to the frame by cleaning off a couple areas on frame and tank before re installing it.I also ran a 12g. grounding wire from tank to frame as an added precaution.Ran wires from dash guage to unit as instructed by the Big Dog (wire was installed with new harness).Still get no action at the guage!! Is there a way to remove the guage and test it to see if it is indeed working properly? Thanks in advance to all that can advise,Jay

To test your gas gauge, remove it from the instrument panel. Using a 6 volt power supply, like your 6 volt car battery, attach one clip lead to the terminal on the back of the gas gauge that is marked "Ignition". Clip the other end of the lead to the positive terminal on your battery. With a second clip lead, connect it to the negative terminal on the battery and then touch the other end of the clip lead to the housing on the gas gauge to complete the ground. The gas gauge needle should move from empty to full when the negative lead is touched to the housing on the gas gauge. If the needle doesn't move your gas gauge is probably defective.

To test the sending unit (even though it is new you should have tested it before installing the unit in the tank), remove the sending unit from the tank and, using an analog multi-meter on the 1X ohm setting, attach the positive lead to the terminal on the sending unit. Attach the negative lead to the housing on the sending unit. Move the float assembly up and down manually and in doing so the needle on the multi-meter should move up and down as well. If the needle doesn't move your sending unit is defective.

Hello jay32249,
Well, there's a few unknowns to figure out before real troubleshooting begins. What is your fuel guage indicating? Is there fuel in the tank and how much? Have you 6 volts to the guage and battery negatively grounded to the frame? Are the connections at the guage correct? If, after these are verified and the problem still exists, suspect sending unit and or guage. Ohm meter continuity checks should be made for each. My limited knowledge tells me that this system operates with regards to variable resistance within the sending unit. If the only source of power is from the guage, verify that power is at both ends, at the guage and at the sending unit. Side note: Suspected inop guage in a brand new 30 gal. tank. Indicates empty. Serviced with eight gallons fuel and still indicated empty. Pulled sending unit plug to guage and witnessed guage go off scale below empty. Conclusion, fuel level too low to give significant level reading and no problem with guage.

Thanks Dog and Harry----the sending unit was,on the Big Dogs advise,checked before it was installed and seemed to work just fine. I will pull the guage this week and test same.If that works as well then I can only imagine that there is something amiss with wiring,which is definatly possible even though it is a new harness that was installed by a local vintage car restorer who has since passed,or I would take it back to him for this! Thanks again,jay

Let us know what you find.