New Gas Gauge Question

[Travis Blake]

I installed a new gas gauge from Classic Industries which goes from empty to full when the key goes on and there is only a half tank of gas.  The sender is new and grounded when we put in the new tank. Is there a way to calibrate it ? Thanks!

[73_Cuda_4_Me]

Is the new gauge an OEM in-dash unit or newer style? Where did tank/sending unit come from? The gauge is usually matched to the ohms resistance on the sending unit from full to empty... I think your sending unit has too low ohms total causing full scale fuel reading (or float/arm messed up?)...

OR you may not be using 5 volt supply for gauge...

I don't think you can run off 12 volts... did you rewire the gauge?

Seems like the sender should be 10 to 73 ohms (full to empty, respectively), from what I remember... newer units may run 10 to 90 ohms...

[Travis Blake]

Is the new gauge an OEM in-dash unit or newer style? Where did tank/sending unit come from? The gauge is usually matched to the ohms resistance on the sending unit from full to empty... I think your sending unit has too low ohms total causing full scale fuel reading (or float/arm messed up?)...

OR you may not be using 5 volt supply for gauge...

I don't think you can run off 12 volts... did you rewire the gauge?

Seems like the sender should be 10 to 73 ohms (full to empty, respectively), from what I remember... newer units may run 10 to 90 ohms...

The gauge is a reproduction from Classic Industries and it is an in dash unit and the power comes from the voltage limiter on the back side of the gauge panel. The sender  came from Laysons I think the name was.

How do you check the ohm resistance ?

[73_Cuda_4_Me]

Do you have a volt/ohm meter? Some auto stores might let you borrow one, or can get one pretty reasonable for testing (Meijer and Walmart have some around 20 bucks)

You measure the ohms from the tank sender signal wire terminal to tank ground... if that is good, then measure from gauge connection to ground...

If wire is shorted to ground anywhere from gauge to tank, gas meter will peg at full (voltmeter reads 0 ohms = no resistance/shorted to ground)... pinched wire, broken insulation, bare wire spot in trunk, etc...

[Topcat]

9-10 gallons should show at half full on the guage.

Bending the float wire may be necessary to get the float calibrated so it reads where you need it to be at.

I used my old one and compared to the new one. Made some slight adjustments,

[Travis Blake]

Is the new gauge an OEM in-dash unit or newer style? Where did tank/sending unit come from? The gauge is usually matched to the ohms resistance on the sending unit from full to empty... I think your sending unit has too low ohms total causing full scale fuel reading (or float/arm messed up?)...

OR you may not be using 5 volt supply for gauge...

I don't think you can run off 12 volts... did you rewire the gauge?

Seems like the sender should be 10 to 73 ohms (full to empty, respectively), from what I remember... newer units may run 10 to 90 ohms...

   Checked the sender unit and got  79.6 and the "old" gauge was 12.4 ....  I haven't gotten into the dash yet to check power and the new gauge

[Travis Blake]

We removed the sender from the tank, disconnected and reconnected the wires, regrounded it, moved the float up and down, and it still spikes to full.

Has anyone else used the repo gauge from Classic Industries?

[73_Cuda_4_Me]

When you disconnect the wire from the sender, does the gauge still peg???

When disconnected at tank, there should be NO fuel reading - stuck at E completely and no movement.

If you still peg with wire disconnected at sending unit, then you have a short in the wire somewhere...

[dodj]

To prove out my gauge when i didn't know if i had a gauge problem or a sender problem was to use a potentiometer.  I disconnected the sender and put a 0 to 100 ohm potentiometer in its place.  Set the pot to 10 ohms and look at the gauge.  Then set it to 40 ohms (should read half). Then set to 70. If your gauge went full sweep.  You have a sender problem.  If it read incorrectly, say, full all the time, you have a gauge or wiring problem.