As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW OF FLT 1052, MKE TO IND, CYCLED THE SURFACE DEICE SYSTEM BEFORE ENTERING ICING CONDITIONS USING AUTOMODE. THE TAIL DEICE ANNUNCIATOR FAILED TO ILLUMINATE. THE CREW TURNED BACK FOR MKE DUE TO HEAVY ICING CONDITONS IN IND. MAINTENANCE FOUND WATER IN AIR LINE TO THE SWITCH. THEY DRAINED THE LINE AND INSTALLED SERVICEABLE PRESSURE SWITCH, OPS CHECKED GOOD. (X)