What was found
(CAN) FLASHES OF THE MGB PRESSURE LIGHT IN FLIGHT. AIRCRAFT LANDED SAFELY. AME SENT ON SITE, NO VISIBLE DAMAGE OR LEAK. MGB PRESSURE SWITCH SUSPECTED TO BE THE CAUSE AND REPLACED. MGB FILTER REPLACED. RUN-UP, LEAK CHECK AND TEST FLIGHT C/O, WITHOUT ANY ADDITIONAL PROBLEM. AIRCRAFT RELEASED. AFTER 6.6 HOURS OF FLIGHT, ON AUG 12, 2010, RE-OCCURRENCE OF THE PROBLEM. TROUBLESHOOTING C/O. WIRING SUSPECTED AND REPAIRED. IN ADDITION, THE NEW SWITCH INSTALLED (S/N 25712) IS DETERMINED TO BE FAULTY (HIGH THRESHOLD), AND REMOVED. THE OLD SWITCH (S/N 21455) IS TESTED, FOUND SERVICEABLE AND RE-INSTALLED. (TC# 20100811003)