As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN)MALFUNCTION OF THE HORIZ STAB SURFACE DE-ICERS WAS SUSPECTED DUE TO FAILURE TO RECOGNIZE A THIRD BUMP AS SHOULD BE INDICATED ON THE PNEUMATIC PRESS GAUGE. FURTHER INVEST REVEALED THAT THE SOLENOID FOR PORT B, WHICH SUPPLIES PRESSURE TO THE HORIZ STAB BOOTS, LOCATED INTERNALLY IN THE DISTRIBUTOR VALVE, WAS NOT BEING ACTIVATED. REPLACEMENT PART WAS SUBSEQUENTLY INSTALLED AND SYS CHECKED OK.