Jack,
I have had a 99PT and now have a 2005PT. We have owned a Beaver since 2001. I have heard numerous complaints about all tank sensors and read-outs being incorrect. The only solution I have heard were to buy outside the tank sensors. Haven't read many complaints about them. I know this doesn't answer your question, but it is a reply that may help you. Don't know if anyone has ever fixed the inside tank sensors Beaver used to install and do not know if that is the type in your rig.
Roy Warren