Overhead Console Temperature Reading Issue

[Eagle71]

I have a 2001 Mountaineer that never came with an overhead console for some reason. Anyway, about 4 years ago, was able to obtain an old console/temp sensor and associated wiring from a junkyard, wired them in, installed all the hardware and viola, temp & compass reading worked great. Until about a month ago. Compass worked fine (and still does), but temp reading would lock in at whatever the ambient temp was after the car warmed up. Next day, same symptoms. Returned to the junkyard, bought a replacement console and temp sensor, and same problem after replacing the old parts with the "new" parts. I tested the new temp sensor, and it's reading about 11-12K ohms - within parameters (so was the old temp sensor fyi). Also rechecked wiring from when I first installed the system, and all checked ok. Bottom line, both old and new consoles work ok until the car warms up, and then the temp reading locks in at whatever the exterior ambient temperature is, and doesn't change (even though the outside air temperature does change). Any suggestions for solution(s)? BTW, I've read previous threads on this general issue, and have soldered the "510" resistor, etc.
Thanks in advance,
Steve