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wittsend
03-16-2014, 10:48 PM
I'm curious if anyone has used resistors to calibrate a gas gauge. I have a situation (not a Studebaker) where I have adapted a gauge package with an engine swap. The oil, water and amps all work because they are common to the engine. However the gas gauge is not common to the tank sender. I get a little over a half tank reading when full and it shows empty when the tank is half full. Since this is a gauge "set" I'd rather not run a separate gauge like a Stewart/Warner.

It seems like the sender has too much resistance. I know when two resistors are run in parallel the value drops (not doubles as many think). Granted one resistor would be fixed while the sender is variable I still think (hope) I can get the gauge a little more accurate. Since the sender runs to ground it seems if I connect a resistor to the sender connection, and then to ground, I'd see some change. Any electrical types out there who can comment.

Thanks, Tom

GinettaG12P
03-16-2014, 11:43 PM
Okay, when the tank is full, the sender should have 240 ohms resistance and when it is empty, it should have 33 ohms. Half full should be about 130 ohms, assuming linearity (which may not be a valid assumption.)

It sound like your sender shows approximately 140 ohms when full and approximately 33 ohms when half full. There is no resistor, either installed in series or in parallel, that will correct both readings.

There are several other possibilities: that the float on the sending unit has become fuel-logged; that there is something in the tank that is impeding the movement of the float arm; that the gauge is not a 240/33 ohm gauge.Okay, when the tank is full, the sender should have 240 ohms resistance and when it is empty, it should have 33 ohms. Half full should be about 130 ohms, assuming linearity (which may not be a valid assumption.)

It sound like your sender shows approximately 140 ohms when full and approximately 33 ohms when half full. There is no resistor, either installed in series or in parallel that will correct both readings.

There are several other possibilities: that the float on the sending unit has become fuel-logged; that there is something in the tank that is impeding the movement of the float arm; that the gauge is not a 240/33 ohm gauge.

junior
03-17-2014, 08:52 AM
I was under the impression that there are two 'standard' ohm ranges for gas gauges...can't remember exactly now, but something like 33-240, and 0-90 ohms. Perhaps look at that possiblilty? junior.

Bud
03-17-2014, 03:16 PM
Resistors won't help you if the gauge only reads at half when the tank is full. Resistors can be used in series with the sending unit if the gauge is reading high, but for a low reading, the sending unit will have to be replaced with the correct part. Bud