What was found
UNABLE TO CONTROL CABIN TEMP. STARTED OUT HOT, ADJUSTED TEMP VERY SMALL AMOUNT ON AFT CABIN CONTROL. CABIN WENT TOO COLD. READJUSTED TOWARD WARM, GOT REALLY HOT. RAN CABIN HOT QRH, TURNED OFF TRIM AIR SWITCH. CABIN TEMP CONTROL WENT BACK TO NORMAL. GROUNDED, YES. CLEANED ALL 3 CABIN & FLIGHT DECK TEMP SENSOR FILTERS, REF B737-900 AMM 21-61-06-100-801. ACCOMPLISHED CABIN TEMPERATURE CONTROL & INDICATION OPS TEST, TEST PASS, NO FAULTS NOTED, REF AMM 21-61-00-700-807-002. TRIM AIR SWITCH ON.