What was found
RIGHT PACK LIGHT ILLUMINATED ON MASTER CAUTION RECALL AFTER ENGINE START. EXTINGUISHES UPON MASTER CAUTION RESET. GROUNDED - YES. C/W BITE TEST AND CONFIRMED RAM AIR ACT RED LIGHT ILLUMINATED ON PZTC #2, FAULT CLEARED SUCCESSFULLY. REPLACED ACAU #2 WITH SERVICEABLE UNIT. INSTALLATION TEST PASSED AND RAM AIR SYSTEM TEST PASSED. C/W PZTC #2 BITE NOTING THE RAM AIR SNSR RED LIGHT ILLUMINATED = INDUCED BY THE RAM AIR SYSTEM TEST. CLEARED FAULT SUCCESSFULLY. RH PACK SYSTEM OPS CHECKS OK. REF B737-800 AMM 21-51-00 & 21-51-02.