Fuel System: Testing '51 champion fuel guage

[cvytrk]

How do I test a fuel guage that is not installed in the car? I want to bench test a guage before I install it in the car. I have a multi-meter and hopefully that is the only tool I'll need. NOTE, I want to test the fuel guage, not the tank sending unit. The only info I found in the service manual is for testing a guage that is already installed in a car. I appreciate all help.

Thanks

[greyben]

I checked resistance readings on a NOS '55 gauge which should have essentially identical internals. The values measured are;

Terminal to terminal: 62 ohms
Bottom terminal to ground: 90 ohms
Top terminal to ground: 152 ohms (the sum of the other two)

Your readings should be close allowing for differences between meters, manufacturing tolerances and possible differences between the '51 and '55.

This may not necessarily verify accuracy or even functionality. To do this you would need a voltage source ~7.5 volts, a variable resistor ~0-200 ohms and a few test leads. The gauge case needs to be run to ground also. This could be used to simulate operational conditions. Of course you would also need to know what resistance values should produce a given indication. I can't help with that.

[RadioRoy]

You can also test it in the car. Get a couple of jumper wires with alligator clips on the ends. They sell them at Radio shack.

Disconnect the gauge in the dash and jumper the disconnected wires to the gauge sitting on the hump on the carpet.

[cvytrk]

Greyben and RadioRoy,
Thank you for your responses. Both suggestions should work. After working with old cars for 49 years, one learns that simply because a part is in its original box and is NOS doesn't mean that it is a good working part. I need to check this NOS gauge to see what I have. Again thanks for your input.