What was found
AFTER TAKEOFF, THE RIGHT RED DUCT LIGHT ILLUMINATED. COMPLETED CHECK LISTS AND SHUTDOWN THE RIGHT ENGINE, AIRCRAFT RETURNED TO AIRPORT. FOUND THE RIGHT DE-ICE PRESSURE REGULATING VALVE INSTALLED BACKWARDS, CAUSING BLEED AIR TO VENT INFO FWD WING BOOT FAIRING AREA. REMOVED AND REPLACED VALVE WITH SERVICEABLE UNIT IAW MM 30-10-06. OPERATED DE-ICING SYSTEM, OPS CHECKS GOOD. DUCT LEAK LIGHT DID NOT ILLUMINATE DURING GROUND RUNS.