It would seem very likely that the carwash and the short are related.
The interior temp sensor, located in the center of the dash board, measures the interior temperature, and is used by the automatic climate control. The dash gauge for the exterior temperature, uses the exterior temperature on the front licence plate. I guess we are just talking semantics, I know what you mean now.
Maybe try to trace some wiring around the exterior temp sensor and see if anything is loose. Good luck.
Regards, Lawrence.