As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK DUE TO MASTER WARNING STAB OVERHEAT CAS POSTING IN CLIMB THROUGH 18,000 FT. ANTI ICE SYSTEM WAS ACTIVATED AT APPROXIMATELY 13,000 FT DURING THE CLIMB. THE QRH EMERGENCY TAB #1 FOR STAB OVHT WAS FOLLOWED, ICING CONDITIONS WERE EXITED BY RETURNING TO KBNA. LANDED WITHOUT INCIDENT. R&R P40 RELAY BOX AND OPS TEST OK.