What was found
(CAN) 1ST -NR 1 ENG HEATER ELEMENT UNSERVICEABLE, NO LIGHT INTO BY-PASS DOOR SWITCH, AND ENG ADAPTER HTR NR 1 CAUTION LIGHT, C/B INTAKE LIP ENG NR 1 POP-OUT. FOUND BOTH ELEMENT OF NR 1 INTAKE HTR (SHORTED). NO FAULT FOUND INTO AC (CDS). HTR ELEMENT REPLACED. 2ND - DURING APPROACH, CREW NOTICE A STRONG ELEC BURN SMELL INTO CABIN. NR 1 ENG INTAKE LIP HTR C/B POP-OUT, CAUTION LIGHT ENG ADAPTER HTR SMELL ORIGIN IDENTIFIED BY PILOTS, FIREMEN ASST REQUESTED BEFORE LANDING. AC LAND SAFELY. FOUND ENG AIR INTAKE ADAPTER HTR SHORTED, BURNED. THIS TIME CDS FAULT CODE FOUND 'TMU 3 FAIL', TMU P/N 4100S018-06 REPLACED, S/N 0214 (AERAZUR). COMPLETE SYSTEM TESTED 'S'.