What was found
ENGINE NO 2 FIRE WARNING SWITCH DOES NOT ILLUMINATE ON PREFLIGHT TEST NO. 2 OVERHEAT LT DOES NOT ILLUMINATE. FAULT LT ILLUMINATES. GROUNDED - YES. REF CORRECTIVE ACTION ON TSR711159, ACCOMP FIRE OVERHEAT OPERATIONAL TEST REF B737-800 AMM 26-10-00-710-801 TEST PASS. VERIFIED FAULT STILL PRESENT WITH HIGH RESISTANCE ON D998 24-25. AFTER SHAKING MW0325, RESISTANCE DROP CONSIDERABLY. RESISTANCE FOR RIGHT CORE DETECTOR 2461, LEFT CORE 3041 NUMBERS STAYED SOLID WHEN TAPPING. CONTINUITY CHECK FLUCTUATES WHEN SHAKING MW0325 RIGHT AT THE T LOWER HARNESS GOING TO LEFT CORE. REPLACED MW0325 OLD STYLE HARNESS TO NEW CA243-02 REF AMM 26-11-02-400-802. NOW WITH IN LIMITS REF FIM 26-10 TASK 805. REINSTALLED ENGINE APU FIRE CONTROL MOD, TEST PASS.