What was found
CREW REPORTED- STAB A/ICE FAIL DURING ICE TEST IN THE AIR. WE TESTED TWICE WITH N2 GREATER THAN 86% AND IT FAILED BOTH TIMES. UNDER MAINTENANCE DIRECTION, WE RESET THE STAB BUTTON AND TESTED AGAIN WITH N2 AT 90%. IT FAILED AGAIN. WE TESTED ONE MORE TIME N2 89% AND IT FAILED AGAIN, RESULTING IN A DIVERSION BACK TO LAS DUE TO ICING IN BUR. MX CORR ACTION- REMOVED AND REPLACED STAB A/I PUSHBUTTON SWITCH. PERFORMED ANTI-ICING SYSTEM OPERATIONAL TEST. OPS CHECK GOOD.