What was found
MACH TRIM FAIL LIGHT ILLUMINATED WHILE IN LEVEL FLIGHT AT 37,000 FT. PRESSED MASTER RECALL SWITCH AND LIGHT EXTINGUISHED. GROUNDED - YES. CONFIRMED FAULT, DFCS BITE TEST SHOWS FAULT MSG NR 22-11334 "MACH TRIM 115VAC PROBLEM" FAULT ISOLATION REF B737-900 FIM 22-16 TASK 835. FOUND MACH TRIM AC C/B OUT AT P18-1 PNL, RESET C/B. ACCOMPLISHED MACH TRIM LIBRARY TEST (GP 60); DFCS LAND VERIFY TEST, REF B737-900 AMM 22-11-00 (GP 49); HGS SYSTEM TEST, REF HGS 4000 SMM 34-36-00. OPERATIONS CHECK NORMAL.