What was found
CABIN GOT VERY HOT AFTER TAKEOFF, FLIGHT DECK COLD. AFTER SEVERAL PAX GOT SICK, F/A INFORMED CREW THAT THE CABIN WAS TOO HOT TO CONTINUE. ACFT WAS APPROX 20 MILES OUT OF LGA, ACFT RETURNED TO FIELD. CONTACTED LGA MX. ACFT HAS BEEN WRITTEN UP TWICE BEFORE. DUCTING UNDER FLOOR APPEARS TO BE IN GOOD SHAPE. FLIGHT DECK IS COLD WITH GOOD DUCTING TEMP. LGA HAS SEVERAL BROKE ACFT WILL FERRY TO MDT. CLAMP UNDER DORSAL FIN LOOSE, TIGHTENED AND REMOVED AND REPLACED CONDENSER MIXER.