bench testing a fuel gauge

[bing kunzig]

Is it possible to bench test a fuel gauge, and if so, how?

[macstude]

By all means yes. This applies to any fuel or electric oil pressure gauge. Three connections to make. The gauge case must be grounded. Provide voltage of choice (6 or 12 volt)to gauge hot terminal (ignition ON). To test gauge ground out the "Sender" terminal and the needle should go full sweep to "full". The tank sending unit is a variable resistance to ground. Zero resistance equals "full". Ditto with an electrical oil pressure gauge.

Which ground you use, negative or positive, will depend on the original vehicle configuration ie: 6V pos or 12 Vneg.

53 Starliner modified

[bing kunzig]

Is the procedure the same with the sending unit removed?

[Alan]

You could take a 100 ohm. reostat or pot. to use as a sending unit and a 12 volt power supply like a Heathkit. The crazy thing is if you had all this stuff you would know how to do it.

[bing kunzig]

I do have the sending unit-on the bench with the gauge. Just trying to determine the origin of the problem.

[Alan]

Then take an ohm meter and see if the sending unit measures 0-99 ohms and if there is any jump in the readings as you move the float up and down , the gague should move with the movement of the float.

[Alan]

What is the problem? Gagues are built to work on exactly 12 Volts most cars have a instrument voltage regulator for the gagues. When you start changing the voltages you change the readings too. But is it the readings not accurate, dose it not work , what?

[macstude]

quote:Originally posted by bing kunzig

Is the procedure the same with the sending unit removed?

I assumed that you only wanted to test the gauge, and that it was on the bench, so to speak.

To test the sending unit by itself use a volt ohm meter connected between the sender terminal and ground (sender housing).

Do not feed 12 volts to a 6 volt gauge! Remember that it is the ground resister circuit that "makes" the gauge read scale, NOT voltage!

Good luck

53 Starliner modified