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Monday, October 26, 2009

LP Sending Unit Isn't Sending

I have an 1989 Class A motorhome. The indicator lights for the propane level always register full. The unit worked fine until about a few months ago. Is there a way to reset this or do I have to replace the sender unit? How does that work?
Brian, (Tayors, SC)

Brian, the LP sending unit assembly is attached directly to the horizontal LP container. The mechanical float assembly is situated inside the container and corresponds with the sending unit/gauge which is secured on the outside of the container. The float assembly activates a magnet positioned at the rear of the gauge. The magnet actually moves the needle on the gauge which in turn "sends" the corresponding electrical signal to the monitor panel.

It could be the gauge unit is faulty and is stuck on "full" in which case it will have to be replaced. In some instances, depending on the maker of the monitor panel, a constant "full" indication means the wire to the monitor panel is shorted to ground. On some panels, it could mean there is an electrical "open" in that circuit; the wire is broken somewhere between the gauge on the container and the monitor panel.

To check the gauge itself, carefully remove the two small screws that attach the gauge to the float assembly and move a magnet along the back side of the gauge. The needle should move as you rotate the magnet. If the gauge is operative in this manner, then the problem is in the actual wire which runs to the monitor panel. Unless the fault is quite obvious, it will probably be easier and less time consuming to simply run a new wire from the gauge up to the rear of the monitor panel and splice it in to the LP wire rather than take the time to determine if it's an "open" or a "short." The LP wire is usually colored white with a green stripe around it. There is, of course, the outside chance that the inside mechanical float assembly itself is faulty, though rarely does that happen. If it is the internal float assembly, have a professional technician perform the replacement


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