I am currently working on some stuff for another trailer project, but when I read the numerous comments about these level sensing systems, and then viewed the product data sheets I am tempted to fix your problem first as I currently have a nearly complete level sensing system. However I think a solution must be capable of being used on all existing AS systems. The best think I derived from this site is that depending upon year and type of trailer there are three sensing systems; 1) conductivity probes meaning their are 4 or 5 probes that contact the fluid and cease to work when they get dirty, 2) an exernal tank strip (probably capacitive) that seems very unreliable from this site, and 3) pressure sensor which I already do. Is this correct or am I missing something?
1) I would think conducutivity probe system would work pretty good if probes are clean. There is a way to replace probes with either a single pressure sensor at the lowest probe, or replace all probes with another technology, but not sure people would want to pay for either approach. Is there really any problem with this system other than cleaning probes?
2) The external tank strip, if capacitive would be sensitive to wires going to the sensor or if not shielded, close to any metal like the frame, or if coming loose from the side of the tank, will vary. All these issues can be fixed. Worst case, are people willing to replace the electronic panel if all you had to do is switch wires from the existing panel to the new panel?
3) Pressue sensor is an "electronic device" and "could" be subject to corrosion and if the hole to the pressure sensing element is plugged, it won't work. You have to remove the sensor to clean it, but have to be careful because the sensor can be damaged if hit with too high a pressure (air hose or poking something in the sensor). It sounds like this is not your problems, mostly wiring and poor electronics is by guess. Again, would people be willing to replace the existing panel with a new panel? Does anyone have a number off the sensor?
Any insight anyone can give would be helpful relative to the problems you have. The system "should" be able to tell you the problem if you have a sensor problem, grounding, low voltage, a wiring problem and so forth but ONLY when a possible problem is detected. All your comments are correct, assuming it's not just poor wiring practices, you should not have all these problems.