What was found
NUMBER 1 AIR MANIFOLD FAIL ALERT AT CRZ FL 340 ENG & WING A/ION, PACKS 1 & 3 ON. DIVERTED & LANDED WITHOUT INCIDENT. PERFORMED NR 1 DECAY CHECK, PASSES 9 SEC, 7 SEC MIN IAW AMM 36-00-01-5. PERFORMED AIR SYS TEST, NO FAULTS NOTED. CHECKED AIU & NO RELATED FAULTS. WHEN ACFT BLOCKED IN, CHECKED MFDCU, FOUND LT WING PRESS SWITCH, FAULT BALL LATCHED. RESET MFDU, FAULT BALL CLEARED. PERFORMED TROUBLESHOOTING IAW FIM 36-23-00-2, AMM 36-23-01-2 & AMM36-23-03-5. CHECKED B NUTSON LT WING DIF PRESS SWITCH, CHECKED NORMAL. RAN ENG & SELECTED WING ANTI, ENG ANTI-ICE, ALL PACKS, NO FAULTS NOTED. CHECKED MFDU, NO FAULTS NOTED, OK TO CONTINUE.