What was found
RETURNED TO DEPARTURE DUE TO STRONG ODOR IN THE CABIN THAT SMELLED LIKE BURNING PLASTIC SHORTLY AFTER TAKEOFF. THE ODOR BEGAN TO DISSIPATE THEN RETURNED. FOUND "FAN" AMBER CAUTION ILLUMINATED ON "COND" PAGE. SELECTED CABIN FANS OFF, CAUTION EXTINGUISHED. REMOVED AND INSPECTED CABIN RECIRCULATING FANS 14HG+15HG, FOUND 15HG, RECIRCULATING FAN NR 1, FAILED. R & R FAN 15HG IAW AMM 21-21-51. OPS CHECKED GOOD.