As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHX - air turnback - 6/2/01 - FLT 521 - after takeoff from PHX en route to RNO the flight crew reported the LT air conditioning pack was blowing warm air, not cooling the aircraft and returned to PHX. PHX maintenance troubleshot and found the 35 degree control valve staying open; the 35 degree control valve and sensor were replaced IAW AMM 21-51-30 & 21-51-51; functional checks were good; no further discrepancies noted.