It sounds like a failed sender or float. I'd remove it and see. If you want a sender which reads an accurate 0 to 30 ohms and is designed well, there is a seller on eBay (his ID is renbusan) who sells a sender designed and made in Taiwan that is very good and about $29 last I looked.
That's sorta what I thought might be going on. I'll pull the sender to see. Thanks for the recommendation on the new sender!
