What was found
SMOKE AVIONICS BAY RED CAS: ON CLIMBOUT OF DAL PASSING THROUGH FL210 WE RECEIVED A RED ' SMOKE AVIONICS BAY' CAS MESSAGE. WE DECLARED AN EMERGENCY , ACCOMPLISHED ALL CHECKLISTS AND RETURNED BACK TO DAL. // SIGNOFF// INSTALLED CUSTOMER SUPPLIED NEW SMOKE DETECTOR PN: 473597-1 SN: SAA1336. OPS CHECK GOOD, NO DEFECTS AT THIS TIME. RETURNED AIRCRAFT TO ORIGINAL STATE BY INSTALLING ALL COMPONENTS REMOVED FOR TROUBLESHOOTING AND COMPONENT REPLACEMENT. WORK PERFORMED IN REFERENCE TO GL-6000 AMM 26-14-01.