As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHORTLY AFTER TAKEOFF OF FLIGHT 1035 MKE-RHI THE DEICE BOOTS DID NOT INFLATE AND THE ANNUNCIATOR DID NOT ILLUMINATE. THE CREW MADE AN AIR-TURN-BACK TO MKE. MECHANIC INSPECTED THE DEICE SYSTEM AND FOUND THE LEFT HORIZONTAL BOOT HAD FAILED. MECHANIC REPLACED THE BOOT AND RETURNED THE AIRCRAFT TO SERVICE WITH NO FURTHER DEFECTS.