This post eventually asks the question: "How does this work and what can I do about it". I took the long way there and that becomes apparent, later. There's smart people here and most will converge on a common answer. If not, no foul no harm. I'm back where I started.
I filled my propane tank. Some of you know that thread. After I got back, I started smelling propane whenever I walked behind the rig or opened the propane door and it would quickly dissipate. This happened once before but not to this degree. I figured the increased amount that resulted from the fill (pressure) changed the dynamics and I was getting more of what I thought was someone else. I conducted the ‘smell test’ about three times in the span of an hour and broke out the soapy water. I found a leak. Pic#1
I was able to secure the leak, through sheer dumb luck. I actually had to work the plug back and forth to get it to stop leaking. I don't know why. Definitely right-hand threads. I finally landed on a spot that passed the soapy water test. I tested it for 2 days, found microscopic bubbles and readjusted. No more bubbles (I inspected with a magnifying glass to ensure). The green you see is a result of the soapy water tests and not corrosion.
Here's what I know (rather 'discovered'). When the plug was in its prior position, the gauge sat straight. 1/2 full was at TDC with 1/4 to the left and 3/4 to the right. The way one would expect it to be.
I noticed the gauge had two, round metal receptors on the back. These receptors ride inside the plugs recess where the label is located. It would seem these track a float inside the tank to measure capacity. I suspect that but don't know it.
The gauge only fits on the plug one way. The outside edges of the plug seem keyed, the gauge's plastic clips are 'keyed' to only fit on the plug one way. The gauge is tied to the plug. The gauge also feeds the LPG reading on the interior control panel (see wire splices - I bought it like that). I’m getting different readings depending on how I position the gauge in the propane bay.
Problem: Does someone know how this works and whether I can put this back where it needs to be to be right? I suspect someone positioned the plug so the gauge would be right with total disregard for a potential leak. I find that hard to believe but not completely impossible.