As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE, THE MASTER CAUTION LIGHT ILLUMINATED AND THE PRESSURE CHECKED GOOD. THE CREW DESCENDED AND SLOWED TO 150 KIAS. AT FL180 THE LIGHT EXTINGUISHED. UPON ARRIVAL AT DCA, MAINTENANCE INSPECTED AND ADJUSTED THE OVER CENTER PROXI SWITCH CLEARANCE IN ACCORDANCE WITH DORNIER MAINTENANCE MANUAL 52-00-00. OPERATIONAL CHECKS WERE PERFORMED AND THE AIRCRAFT WAS RELEASED FOR SERVICE.