66 Lemans - Troubleshooting Gas gauge

algtrader

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Dear Lemans forum,

My 66 Lemans gas gauge isn't working - it constantly reads almost full (i.e., the needle is all the way indicating close to full). How do I troubleshoot where the issue is?

Before posting this, I did some readings:
1. There is a 12V wire coming into the gas gauge
2. Then there is a wire coming out from the gas gauge to a harness
3. And I see a wire going into what I think is the gas tank float

So visualizing this, I think the circuit is +12V --> gas gauge --> gas tank float (resistor?) --> ground. Does this sound about right?

If it is what are next steps? I'm stuck right now since I can't play with either the gas gauge or the gas tank float because the circuit is inside the gauge and gas tank respectively.

Hope the above makes sense for some of you. Thank you!
 
Check the ground wire coming from the tank sender, no ground you get a full reading.
 
My issue for my 74 LeMans appears to be somewhere under my dash - more TBD
______________________________
 
Thanks for the replies. I was able to troubleshoot the issue with the attached wiring diagram and cable finder/signal tracer tool.
 

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