Yep, your temp module is borked if it is reading a clean 20 degrees off. You just need a new module. Sorry that I don't have any more available, but 124s in the wrecking yards have completely dried up. I used to have a steady stream of them just a few years ago. I have a LOT of 126 modules, though, and also ONE temp module for an early 124 (1986/1987).