What was found
SMOKE AFT CABIN AREA & TEMP HOT. UPON TAKEOFF CREW NOTICED AN ODD SMELL. UNSURE IF THEY SMELLED DE-ICING FLUID OR NOT. TEMP IN BOTH CABIN & SUPERNUMERARY AREA STARTED TO NOTICEABLY INCREASE. SHORTLY AFTER PHYSICALLY SAW SMOKE IN SUPERNUMERARY AREA. DECLARED AN EMER & RETURNED. COMPLETED RED BORDER COM & NORMAL CHECKLIST. LANDED WITHOUT INCIDENT. REMOVED LT AIR COND PACK TEMP CONTROL VLV IAW MD80 AMM 21-61-01. RE-INSTALLED SAME TEMP CONTROL VLV WHICH OPERATES & LEAK CHECKED GOOD IAW AMM 21-61-01. REMOVED, INSPECTED & RE-INSTALLED LT & RT WATER SEPARATORS. OPERATIONS & LEAK CHECKED GOOD IAW AMM 21-20-02. PERFORMED OPERATIONAL CHECK OF RT TEMP CONTROL IAW AMM21-60-00. OPERATIONS CHECK WAS GOOD, NO DEFECTS NOTED. R & R LT TEMP SENSOR, RATE OF CHANGE HI LIMIT SENSOR. AIR COND SYS OPERATIONS CHECKED GOOD IAW AMM 21-60-00 BUT SYS DOES NOT AUTO SHUTDOWN. FOUND GND WIRE LOOSE FOR LT THERMAL SWITCH FOR AUTO SHUTDOWN. TIGHTENED GND WIRE CONNECTION. AUTO SHUTDOWN SYS OPERATIONS CHECKED GOOD IAW AMM 21-31-04. ACFT RETURNED TO SERVICE.