Well my Propane tank gauge has been staying slightly above empty for at least a year. I know there is some fuel still in there. I used both the refrigerator and the furnace at the Shawnee rally the gauge never moved after two weeks. I haven't filled the tank for about two years so it should be somewhere around 1/2 full or slightly less.

Today I decided to find the problem. I removed the wire from the sending unit on the tank and the gauge in the coach went to full scale one way. I then jumpered the sending unit wire to ground and it went full the opposite direction. So the wiring and the inside the coach gauge are working. (I forget which way is full and which is empty).

I removed the sender and cleaned the mounting (ground side) and also the terminal where the wire goes. I put an ohm meter across the sending unit and with a magnet across the back I moved the gauge from empty to full and back again. I got the expected readings between 0 and 90 ohms. So the sending using unit also looks good.

Not knowing exactly how much fuel is in the tank I set the gauge to 1/2 and remounted it. Now that it is mounted it still reads 1/2. If I remove it and set it to 3/4, then it stays at 3/4 when remounted.

So here is my question. How do I get the sender to re-sync with the float (and magnet) inside the tank?

I plan to go for a ride and bounce the liquid around inside the tank to see if that helps re-sync the float to the sending unit again.

Thanks Bruce and Richard.

Richard, After reading your suggestion on clearance on the rear of the sender, I got another idea. How about I take some clay and put it behind the sensor to determine exactly how much gap is there. Then remove the clay and fashion a steel shim much like a washer and fill that gap. Now the magnetic flux lines travel through steel which is a much better conductor than air.
<snip>

Thanks Bruce and Richard.

Richard, After reading your suggestion on clearance on the rear of the sender, I got another idea. How about I take some clay and put it behind the sensor to determine exactly how much gap is there. Then remove the clay and fashion a steel shim much like a washer and fill that gap. Now the magnetic flux lines travel through steel which is a much better conductor than air. I already polished the back of the sender and the place where it goes on the tank with scotch brite and a dremmel tool wire brush. So those surfaces are clean and shiny.

Thanks again for the ideas. I do not want to cut down and possibly destroy the existing sensor as a new one is $60.00. Now if I had an old tank to take one off of that would be a different story.