CNG gas guage mostly on full

[Ted1207]

90% of the time my 2000 f150 bi-fuel gas gauge reads full, even as I'm running completely out of fuel. I do try and watch the mileage, but sometimes it bites me. I suppose the sending unit is responding to the pressure in the tank. That being said, is there anything a Saturday mechanic (me) can do to specifically isolate any issues. For instance, are there contacts to be disconnected, cleaned with contact cleaner, and reconnected? Or anything else to do? If not, what's the cost of a sending unit and where is it located? Anything else I need to know?
Thanks in advance...

[maxman]

Re: CNG gas guage mostly on full

Is the gauge reading full on both gasoline and cng, when the tanks are both less than full? If it is misreading on both fuels, it's not the senders, but could actually be the gauge itself.

[Ted1207]

Re: CNG gas guage mostly on full

Unleaded gas reading is OK, just the CNG